Community Mitigation Guidelines to Prevent Pandemic Influenza

Morbidity and Mortality Weekly Report Recommendations and Reports / Vol. 66 / No. 1 April 21, 2017 Community Mitigation Guidelines to Prevent Pandemic Influenza — United States, 2017 Continuing Education Examination available at http://www.cdc.gov/mmwr/cme/conted.html. U.S. Department of Health and Human Services Centers for Disease Control and Prevention

Recommendations and Reports CONTENTS Disclosure of Relationship Introduction ............................................................................................................1 CDC, our planners, or content experts, and their spouses/ Purpose .....................................................................................................................2 partners wish to disclose they have no financial interests or other relationships with the manufacturers of commercial Background .............................................................................................................2 products, suppliers of commercial services, or commercial Methods ....................................................................................................................9 supporters. Planners have reviewed content to ensure there Recommendations on the Use of Personal, Community, and is no bias. Environmental NPIs ......................................................................................... 11 Content will not include any discussion of the unlabeled use Discussion ............................................................................................................. 19 of a product or a product under investigational use, with the Conclusion ............................................................................................................ 21 exception that some of the recommendations in this document References ............................................................................................................. 21 might be inconsistent with package labeling CDC did not accept commercial support for this continuing education activity. The MMWR series of publications is published by the Center for Surveillance, Epidemiology, and Laboratory Services, Centers for Disease Control and Prevention (CDC), U.S. Department of Health and Human Services, Atlanta, GA 30329-4027. Suggested citation: [Author names; first three, then et al., if more than six.] [Title]. MMWR Recomm Rep 2017;66(No. RR-#):[inclusive page numbers]. Centers for Disease Control and Prevention Anne Schuchat, MD, Acting Director Patricia M. Griffin, MD, Acting Associate Director for Science Joanne Cono, MD, ScM, Director, Office of Science Quality Chesley L. Richards, MD, MPH, Deputy Director for Public Health Scientific Services Michael F. Iademarco, MD, MPH, Director, Center for Surveillance, Epidemiology, and Laboratory Services MMWR Editorial and Production Staff (Serials) Sonja A. Rasmussen, MD, MS, Editor-in-Chief Martha F. Boyd, Lead Visual Information Specialist Charlotte K. Kent, PhD, MPH, Executive Editor Maureen A. Leahy, Julia C. Martinroe, Christine G. Casey, MD, Editor Stephen R. Spriggs, Tong Yang, Teresa F. Rutledge, Managing Editor Visual Information Specialists David C. Johnson, Lead Technical Writer-Editor Quang M. Doan, MBA, Phyllis H. King, Terraye M. Starr, Moua Yang, Catherine B. Lansdowne, MS, Project Editor Information Technology Specialists MMWR Editorial Board Timothy F. Jones, MD, Chairman William E. Halperin, MD, DrPH, MPH Jeff Niederdeppe, PhD Matthew L. Boulton, MD, MPH King K. Holmes, MD, PhD Patricia Quinlisk, MD, MPH Virginia A. Caine, MD Robin Ikeda, MD, MPH Patrick L. Remington, MD, MPH Katherine Lyon Daniel, PhD Rima F. Khabbaz, MD Carlos Roig, MS, MA Jonathan E. Fielding, MD, MPH, MBA Phyllis Meadows, PhD, MSN, RN William L. Roper, MD, MPH David W. Fleming, MD Jewel Mullen, MD, MPH, MPA William Schaffner, MD

Recommendations and Reports Community Mitigation Guidelines to Prevent Pandemic Influenza — United States, 2017 1 Noreen Qualls, DrPH 2 Alexandra Levitt, PhD 1,3 Neha Kanade, MPH Narue Wright-Jegede, MPH1,4 Stephanie Dopson, ScD5 6 MatthewBiggerstaff, MPH Carrie Reed, DSc6 Amra Uzicanin, MD1 1Division of Global Migration and Quarantine, National Center for Emerging and Zoonotic Infectious Diseases, CDC, Atlanta, Georgia 2Office of Infectious Diseases, CDC, Atlanta, Georgia 3Eagle Medical Services, San Antonio, Texas 4 Karna, Atlanta, Georgia 5Division of State and Local Readiness, Office of Public Health Preparedness and Response, CDC, Atlanta, Georgia 6Influenza Division, National Center for Immunization and Respiratory Diseases, CDC, Atlanta, Georgia Summary When a novel influenza A virus with pandemic potential emerges, nonpharmaceutical interventions (NPIs) often are the most readily available interventions to help slow transmission of the virus in communities, which is especially important before a pandemic vaccine becomes widely available. NPIs, also known as community mitigation measures, are actions that persons and communities can take to help slow the spread of respiratory virus infections, including seasonal and pandemic influenza viruses. These guidelines replace the 2007 Interim Pre-pandemic Planning Guidance: Community Strategy for Pandemic Influenza Mitigation in the United States — Early, Targeted, Layered Use of Nonpharmaceutical Interventions (https://stacks.cdc.gov/view/ cdc/11425). Several elements remain unchanged from the 2007 guidance, which described recommended NPIs and the supporting rationale and key concepts for the use of these interventions during influenza pandemics. NPIs can be phased in, or layered, on the basis of pandemic severity and local transmission patterns over time. Categories of NPIs include personal protective measures for everyday use (e.g., voluntary home isolation of ill persons, respiratory etiquette, and hand hygiene); personal protective measures reserved for influenza pandemics (e.g., voluntary home quarantine of exposed household members and use of face masks in community settings when ill); community measures aimed at increasing social distancing (e.g., school closures and dismissals, social distancing in workplaces, and postponing or cancelling mass gatherings); and environmental measures (e.g., routine cleaning of frequently touched surfaces). Several new elements have been incorporated into the 2017 guidelines. First, to support updated recommendations on the use of NPIs, the latest scientific evidence available since the influenza A (H1N1)pdm09 pandemic has been added. Second, a summary of lessons learned from the 2009 H1N1 pandemic response is presented to underscore the importance of broad and flexible prepandemic planning. Third, a new section on community engagement has been included to highlight that the timely and effective use of NPIs depends on community acceptance and active participation. Fourth, to provide new or updated pandemic assessment and planning tools, the novel influenza virus pandemic intervals tool, the Influenza Risk Assessment Tool, the Pandemic Severity Assessment Framework, and a set of prepandemic planning scenarios are described. Finally, to facilitate implementation of the updated guidelines and to assist states and localities with prepandemic planning and decision-making, this report links to six supplemental prepandemic NPI planning guides for different community settings that are available online (https://www.cdc.gov/nonpharmaceutical-interventions). Introduction actions that persons and communities can take to help slow Nonpharmaceutical interventions (NPIs) are strategies for the spread of respiratory viruses (e.g., seasonal and pandemic disease, injury, and exposure control (https://www.cdc.gov/ influenza viruses). These actions include personal protective phpr/capabilities/DSLR_capabilities_July.pdf). They include measures for everyday use (e.g., staying home when ill, covering coughs and sneezes, and washing hands often) and communitywide measures reserved for pandemics and aimed at Corresponding author: Noreen Qualls, Division of Global Migration reducing opportunities for exposure (e.g., coordinated closures and Quarantine, National Center for Emerging and Zoonotic Infectious and dismissals of child care facilities and schools and cancelling Diseases, CDC. Telephone: 404-639-8195; E-mail: [email protected]. mass gatherings). When a novel influenza A virus with US Department of Health and Human Services/Centers for Disease Control and Prevention MMWR / April 21, 2017 / Vol. 66 / No. 1 1

Recommendations and Reports pandemic potential emerges, NPIs can be used in conjunction is how and when to implement community-level NPIs that with available pharmaceutical interventions (antiviral might be warranted but are more disruptive (e.g., temporary medications) to help slow its transmission in communities, school closures and dismissals, social distancing in workplaces especially when a vaccine is not yet widely available. Given and the community, and cancellation of mass gatherings) current vaccine technology, a pandemic vaccine might not (Table 1). These decisions are made by state and local officials be available for up to 6 months (https://www.fda.gov/%20 on the basis of conditions in the applicable jurisdictions, with ForConsumers/ConsumerUpdates/ucm336267.htm). NPIs guidance from CDC (according to pandemic severity and can be used before a pandemic is declared in areas where a potential efficacy) and governing authorities (1). Prepandemic novel influenza A virus is detected and during a pandemic. planning, along with community engagement, is an essential These 2017 guidelines provide evidence-based component of these decisions (Table 2). recommendations on the use of NPIs in mitigating the The decision regarding whether and when to recommend effects of pandemic influenza. These guidelines update additional NPIs is another component (Table 3). State and and expand the 2007 strategy (https://stacks.cdc.gov/view/ local public health departments might use certain influenza cdc/11425).* surveillance indicators to help decide when to consider implementing NPIs such as school closures and dismissals and other social distancing measures in schools, workplaces, Purpose and public settings during an influenza pandemic. The choice The purpose of these guidelines is to help state, tribal, local, of influenza surveillance indicators might differ among states and territorial health departments with prepandemic planning and localities, depending on the availability and capacity of and decision-making by providing updated recommendations their public health resources. Examples of possible influenza on the use of NPIs. These recommendations have incorporated surveillance indicators include additional patient visits to lessons learned from the federal, state, and local responses to health care providers for influenza-like illness (ILI) and the influenza A (H1N1)pdm09 virus pandemic (hereafter increased geographic spread of influenza within a state. referred to as the 2009 H1N1 pandemic) and findings from Indicators for school closures and dismissals might include research. Communities, families and individuals, employers, increased school absenteeism rates or the earliest laboratory- and schools can create plans that use these interventions to help confirmed influenza cases among students, teachers, or staff slow the spread of a pandemic and prevent disease and death. members. Indicators that might help confirm that NPI Specific goals for implementing NPIs early in a pandemic implementation should continue include increased influenza- include slowing acceleration of the number of cases in a associated hospitalizations or increases in adult or pediatric community, reducing the peak number of cases during the deaths attributed to influenza. Additional information about pandemic and related health care demands on hospitals NPI prepandemic planning is available (supplementary and infrastructure, and decreasing overall cases and health Chapter 1 https://stacks.cdc.gov/view/cdc/44313). effects (Figure 1). When a pandemic begins, public health authorities need to decide on an appropriate set of NPIs for Background implementation and to reiterate the importance of personal protective measures for everyday use (e.g., voluntary home An influenza pandemic occurs when a novel virus emerges for isolation of ill persons [staying home when ill], respiratory which the majority of the population has little or no immunity. etiquette, and hand hygiene) and environmental cleaning Influenza pandemics are facilitated by sustained human-to- measures (e.g., routine cleaning of frequently touched human transmission, and the infection spreads worldwide over surfaces), which are recommended at all times for prevention a relatively short period (2). The first influenza pandemic of of respiratory illnesses (Table 1). Personal protective measures the 21st century began in 2009, 2 years after the 2007 strategy reserved for pandemics (e.g., voluntary home quarantine of for prepandemic planning was published. Lessons learned exposed household members [staying home when a household during the response to the 2009 H1N1 pandemic underscored member is ill] and use of face masks by ill persons) also the importance of a flexible approach to the use of NPIs, might be recommended (Table 1). A more difficult decision particularly during the early stages of a pandemic, and led to the development of new tools for assessing pandemic severity * The updated 2017 planning guidelines do not address pandemic vaccine and prepandemic planning (Box 1). development and distribution, use of respirators in community or health care settings during a pandemic, or travel restrictions during a pandemic. Guidance and policies in these areas will be developed separately, as needed. 2 MMWR / April 21, 2017 / Vol. 66 / No. 1 US Department of Health and Human Services/Centers for Disease Control and Prevention

Recommendations and Reports FIGURE 1. Goals of community mitigation for pandemic influenza Slow acceleration of number of cases Pandemic outbreak: Reduce peak number of cases no intervention and related demands on hospitals and infrastructure Daily number of cases Reduce number of overall cases and health effects Pandemic outbreak: with intervention Number of days since first case Source: Adapted from: CDC. Interim pre-pandemic planning guidance: community strategy for pandemic influenza mitigation in the United States—early, targeted, layered use of nonpharmaceutical interventions. Atlanta, GA: US Department of Health and Human Services, CDC; 2007. https://stacks.cdc.gov/view/cdc/11425. Lessons Learned from the 2009 H1N1 the 2009 pandemic influenza A virus turned out to be a novel Pandemic Response H1N1 virus that appears to have emerged in southern Mexico and was first identified in two persons in California (13). Although The 2009 H1N1 pandemic was a reminder to be prepared the 2009 H1N1 pandemic in the United States was moderate in for the unpredictable nature of pandemics. Knowing in advance terms of overall morbidity and mortality among the U.S. general which subtype of pandemic virus will emerge is impossible, population, severe outcomes from H1N1pdm09 virus infection as is where and when it will emerge, how quickly the virus were more common among children, young adults, and specific will spread, how severe the illness will be, and who will be the groups at risk for serious complications (e.g., pregnant women) most affected. Because of this unpredictability, prepandemic than among older adults (Box 1). planning must be broad and flexible. Although the emergence of the H1N1pdm09 virus prompted The 2007 strategy for prepandemic planning was developed development of pandemic vaccines, a pandemic vaccine was with the assumption that the next influenza pandemic would not available until October 2009, 6 months after the initial be severe, like the 1957 pandemic, which was characterized by report that identified the pandemic virus. In addition, another high transmissibility and medium clinical severity. When the 2 months were required (December 2009) for sufficient stocks 2007 strategy was developed, the primary concern was that a to be manufactured, distributed, and available to vaccinate pandemic virus might evolve from the highly pathogenic avian several population groups, including school-aged children and influenza A (H5N1) virus, a virus that reemerged in Asia in persons living with or caring for infants aged <6 months, as 2003 in domestic poultry and spread to Africa, the Middle East, recommended by the Advisory Committee on Immunization and Europe among poultry, with sporadic zoonotic transmission † Practices (ACIP). Even though work is ongoing to accelerate (37). Moreover, CDC thought that this virus would most likely † emerge overseas, providing the United States with time to prepare In July 2009, ACIP recommended vaccination of several population groups, for a domestic response, including making use of prepandemic including children aged 6 months through 18 years because cases of H1N1 influenza H5N1 vaccine in CDC’s Strategic National Stockpile. Instead, had occurred in children who were in close contact with each other in school and child care settings (https://www.cdc.gov/h1n1flu/vaccination/acip.htm). US Department of Health and Human Services/Centers for Disease Control and Prevention MMWR / April 21, 2017 / Vol. 66 / No. 1 3

Recommendations and Reports BOX 1. Lessons learned from the 2009 H1N1 pandemic response The 2009 H1N1 pandemic demonstrated the Public health tools to assess pandemic severity and unpredictable nature of influenza viruses and showed that guide NPI selection prepandemic planning must be broad and flexible. Lessons The 2007 Pandemic Severity Index had limited usefulness learned during the 2009 H1N1 pandemic response from because attack rates and case-fatality ratios were difficult to the United States and other affected countries follow. measure and imprecise early in the pandemic. H1N1 and children • The earliest available data on attack rates and case- The epidemiology of pandemic influenza might fatality ratios suggested that the 2009 H1N1 pandemic be different from the epidemiology of seasonal virus was highly transmissible and caused severe influenza; therefore, different populations might be outcomes. However, the cases being reported disproportionately affected. overestimated severity because they were primarily • An estimated 43–89 million people in the United States derived from mortality data. were infected with H1N1pdm09 virus during • By May 1, 2009, which was 5 days after the U.S. April 2009–April 2010, and approximately 12,000 Department of Health and Human Services (HHS) people died (3). declared a nationwide public health emergency, CDC • Severe outcomes of influenza include complications had received reports of 141 laboratory-confirmed that require hospitalization and can be fatal (e.g., H1N1pdm09 cases in 19 states, with one death in Texas pneumonia or bronchitis). Severe outcomes from (https://www.cdc.gov/h1n1flu/updates/050109.htm). H1N1pdm09 virus infection were most common On the basis of this initial information and continued among children, young adults, and specific groups reports of cases of disease with severe outcomes in at high risk for complications (e.g., pregnant women) Mexico, including deaths among previously healthy rather than in adults aged ≥65 years, the group most young adults (11), CDC recommended that at risk from seasonal influenza (4–7). Over the course communities with laboratory-confirmed cases of of the pandemic, an estimated 86,000 children were H1N1pdm09 virus consider closing child care facilities hospitalized in the United States, which is 2–3 times and schools, depending on the extent and severity of the number admitted during a typical influenza illness (12). CDC also recommended other NPIs season (5). The number of deaths among children described in the 2007 strategy, including voluntary also was more than twice as high as during a regular home isolation for ill persons (i.e., staying home when influenza season. ill) and voluntary home quarantine for exposed • On August 28, 2009, the Advisory Committee on household members (i.e., staying home when a Immunization Practices recommended that children household member is ill). be placed higher on the priority list for receiving the • Within 12 days of recognition of the emerging monovalent H1N1 vaccine, which became available in pandemic, the national influenza surveillance system October 2009 (8). generated sufficient data for a refined assessment. • Children at risk for severe outcomes from the – From April 23, 2009, when H1N1pdm09 virus was H1N1pdm09 virus (and from any influenza virus) detected in California (13), through May 5, 2009, included those with underlying health conditions such CDC received reports of 403 confirmed cases of as asthma, diabetes, obesity, or heart, lung, or H1N1pdm09 virus in 38 states. The low rates of neurologic diseases. Approximately 60% of hospitalized hospitalizations and deaths, as well as reported attack children had one or more of these conditions, rates similar to those for seasonal influenza, compared with 80% of hospitalized adults (5). Infants suggested that the majority of U.S. cases were less born to mothers infected with the H1N1pdm09 virus severe than those reported from Mexico. also might have been at risk, as suggested by U.S. and – CDC issued new nonpharmaceutical intervention Canadian studies which found that infants whose (NPI) guidance on May 5, 2009 (14), recommending mothers received the H1N1 vaccine were less likely that although ill students and teachers should stay to be small for their gestational age or delivered home, schools did not need to close. The guidance preterm (9,10). acknowledged that public health authorities in certain jurisdictions might still decide to close 4 MMWR / April 21, 2017 / Vol. 66 / No. 1 US Department of Health and Human Services/Centers for Disease Control and Prevention

Recommendations and Reports BOX 1. (Continued) Lessons learned from the 2009 H1N1 pandemic response schools on the basis of local considerations, dates for schools ranged from early August through including public concern, school absenteeism, and early September (17). A comparison of Texas school staffing shortages. districts that closed versus those that stayed open – During August–December 2009, communities in during the pandemic found that school closure was 46 U.S. states implemented 812 dismissal events associated with a 45%–72% reduction in acute (i.e., a single school dismissal or dismissal of all respiratory illness in households with school-aged schools in a district), affecting 1,947 schools with children (18). approximately 623,616 students and 40,521 – Mathematical models suggested that school closures teachers (15). The 1,947 schools included 639 urban in Alberta, Canada, in May 2009 were associated and 1,250 rural schools, representing 0.7% and with reduced transmission among school children 3.3% of all urban and rural schools, respectively, in by approximately 50%, attenuating the first wave the United States. of the 2009 H1N1 epidemic (19). • The recognition that the Pandemic Severity Index was – H1N1pdm09 virus transmission in the greater of limited use during the earliest stages of an actual Mexico City, Mexico, area decreased by an estimated pandemic led to the development of a new tool for 29%–37% after school closures and implementation evaluating the potential effects of an emerging of other social distancing measures (20). pandemic, the Pandemic Severity Assessment – After conducting a systematic review of scientific Framework (PSAF) (supplementary Chapter 2 https:// literature published through February 2011, stacks.cdc.gov/view/cdc/44313). including initial data gathered during the 2009 NPIs and influenza transmission H1N1 pandemic, the U.S. Community Preventive Well-established methods to prevent seasonal influenza Services Task Force found insufficient evidence to transmission, such as hand hygiene promotion, also were determine whether the public health benefits of effective in pandemic influenza settings to prevent the preemptive, coordinated school dismissals balanced spread of H1N1pdm09 virus in some communities. their economic and social costs during a mild or • Hand hygiene. A randomized trial, conducted over moderate influenza pandemic. However, the task 12 weeks in 60 elementary schools in Cairo, Egypt, force did recommend preemptive, coordinated during the 2009 H1N1 pandemic, demonstrated a school dismissals during a severe pandemic (21). 47% reduction in confirmed cases of influenza after • Social distancing measures. H1N1pdm09 virus twice-daily hand washing and health hygiene instruction transmission in Mexico decreased significantly after in comparison with a control group that did not receive school closures and implementation of other social health hygiene instruction or have access to soap and distancing measures (20,22). In the United States, hand-drying materials (16). This study demonstrated schools in Georgia that shortened school days had less the effects of hand washing on laboratory-confirmed absenteeism due to severe respiratory illness (23). influenza in a population of persons that typically have Additional assessments are needed to determine the value little or no access to soap or hand-drying materials and of combining voluntary home quarantine with antiviral among whom frequent hand washing is not standard. chemoprophylaxis. • School closures and dismissals. Data from the United • Although the 2007 strategy suggested that communities States, Canada, and Mexico suggest that early consider combining voluntary home quarantine with implementation of school closures and dismissals prophylactic use of antiviral medications, assuming a reduced the spread of H1N1pdm09 virus. feasible means of distribution, HHS did not adopt – Two waves of the 2009 H1N1 pandemic occurred antiviral chemoprophylaxis as its official policy because of in the United States, one in spring 2009 and one in concerns about insufficient supplies and drug resistance. fall 2009. The majority of pandemic cases occurred • During the 2009 H1N1 pandemic, antiviral during the fall wave (4), as H1N1pdm09 cases chemoprophylaxis of exposed persons contained the surged in many U.S. communities about 2 weeks spread of the disease, along with the implementation after schools reopened after summer break. Opening of social distancing measures, in a few small, well- defined settings, including a summer camp (24) and a US Department of Health and Human Services/Centers for Disease Control and Prevention MMWR / April 21, 2017 / Vol. 66 / No. 1 5

Recommendations and Reports BOX 1. (Continued) Lessons learned from the 2009 H1N1 pandemic response cruise ship (25). Moreover, an observational cohort care center or school closed temporarily in response to study of 259 households in the United Kingdom found the 2009 H1N1 pandemic, 90% of parents agreed with that administration of antiviral medications to 285 the dismissal decision, and 85% believed the dismissal confirmed patients and their 761 close contacts was reduced influenza transmission (27,28). very effective (92%) in preventing household – A total of 75% of parents who responded stated that transmission (26). the dismissal was not a problem, and 3% stated it • Although limited, the H1N1pdm09 experience suggests was a major problem. Approximately 20% of parents that antiviral chemoprophylaxis might be recommended reported that an adult in the household missed work in the future in some settings as an adjunct to self- because of the dismissal, and 19% had a child who quarantine, assuming that additional antiviral missed a free or reduced-cost lunch. Of these, 2% medications are on the market, providing more treatment and <1%, respectively, said missing work and choices and making the emergence of drug resistance missing lunch were major problems. less of a concern. However, this recommendation would – Most of the 523 parents polled believed that at least require much greater quantities of antiviral medications, one of the following factors was a major reason the even if no new products are developed, to ensure institution had closed: 1) to keep children apart and sufficient supplies. reduce the chance they would infect each other Mobilizing the public (81%), 2) because the school decided cleaning the Most members of the public complied with public building and surfaces that children touch was health recommendations regarding hand hygiene and important for reducing the spread of the illness social distancing. (73%), and 3) because the school or child care center • The Harvard Opinion Research Program conducted could not operate effectively when numerous 13 polls on the response of the U.S. public during the students were absent (58%). 2009–2010 pandemic, including the response of the • A study conducted through an online survey of school general public, pregnant women, new mothers, parents, principals showed that implementing NPIs in public and businesses. These randomized telephone polls schools in New York City, New York, was feasible during found the following: the 2009 H1N1 pandemic (29). Schools successfully – A total of 59% of 1,067 Americans reported washing implemented respiratory etiquette education, hand- their hands or using hand sanitizer more frequently hygiene measures, and environmental measures and during the 2009 H1N1 pandemic (27). A total of isolated ill students. Another online survey found that 25% avoided places where numerous people tend the majority of public schools in Georgia also were able to gather, such as sporting events, malls, or to successfully implement both personal and community public transportation. NPIs recommended by CDC (23). – Most (85%) of 514 pregnant women washed or Public health practitioners should be prepared to explain sanitized their hands more frequently to reduce the that the initial pandemic guidance might change if a chance of infection with H1N1pdm09 virus (27). pandemic is more or less severe than initially assessed. A total of 68% reported taking steps to avoid • Within 12 days of recognizing the emerging pandemic proximity to someone who had influenza-like on April 23, 2009, CDC updated its initial guidance symptoms, and 31% avoided mass gathering places. on NPIs (issued on May 1, 2009) on May 5, 2009, on Most (91%) of 526 new mothers also washed or the basis of more complete and robust data that sanitized their hands more frequently, and 81% took suggested that the majority of U.S. cases were less severe steps to avoid being near someone who had than those reported from Mexico. influenza-like symptoms. • Certain public health departments reported difficulties School-related NPIs, including school closures and in communicating the updated guidance on school dismissals, were acceptable and feasible. closures to their communities, especially communities • According to a Harvard Opinion Research Program that were planning to implement school closures or had poll of 523 parents from 39 U.S. states whose child already done so (30,31). 6 MMWR / April 21, 2017 / Vol. 66 / No. 1 US Department of Health and Human Services/Centers for Disease Control and Prevention

Recommendations and Reports BOX 1. (Continued) Lessons learned from the 2009 H1N1 pandemic response • The H1N1pdm09 experience with school closures required advanced planning and preparation, as well suggests the need to coordinate and harmonize school as high-level political leadership; collaboration between closure policies across jurisdictions and to proactively public health and emergency management agencies; communicate and explain any jurisdictional differences. coordination with businesses, nongovernmental Public engagement, community preparedness, and trust organizations, and community- and faith-based in government action are important for successful NPI organizations; and transparent communication with implementation during a pandemic. the public (34). • Practical obstacles to NPI implementation that • During future pandemics, local health policies and risk required community-level solutions included 1) ill communication strategies should take into account persons going to work because they lacked unpaid leave community attitudes and acceptance of preventive (32), 2) lack of clarity about decision-making authority behaviors related to social distancing, hand hygiene, to close schools for public health reasons in some and vaccination, which might differ across racial and jurisdictions (30,33), and 3) lack of access to clean economic groups (35). water, soap, or hand sanitizer in some workplaces. • According to an online survey of a nationally • Although 74% of 1,057 businesses that participated representative sample conducted by the University of in a Harvard Opinion Research Program poll on Maryland, clear and consistent communication by business preparedness for the H1N1pdm09 virus public health authorities and government spokespersons, offered paid sick leave for at least some workers (27), including the use of role models, was important to the fewer offered paid leave that would allow workers to public’s trust in government actions during the 2009 take care of ill family members (35%) or to take time H1N1 pandemic (36). Although the University of off to care for children if schools or child care centers Maryland study focused on risk communications closed (21%). related to H1N1 vaccination, this finding also is likely • In large cities such as New York City, New York, rapid to apply to public attitudes about NPI implementation. implementation of local-level response strategies the pace of development, distribution, and administration of Community Engagement a vaccine during future pandemics, this experience reaffirmed The 2009 H1N1 pandemic underscored that effective the importance of the use of NPIs in the early stages of a prepandemic planning requires the involvement of public health pandemic before a well-matched vaccine is widely available and local leaders, employers, organizations, and stakeholders (i.e., vaccines produced using a virus that is very similar to the and is essential to ensure timely and effective use of NPIs to circulating virus). limit disease spread during a pandemic (Box 2). Effective use of Another lesson learned about NPI implementation during NPIs depends on the acceptance and participation of individual the 2009 H1N1 pandemic was that rapidly changing guidance persons who implement personal protective measures and of can create confusion and difficulties during implementation communities that implement communitywide measures such (Box 1) (30,31). Nevertheless, field studies found that school- as temporary school closures (https://www.cdc.gov/phpr/ related NPIs, including school closures recommended to capabilities/DSLR_capabilities_July.pdf). mitigate the impact of the 2009 H1N1 pandemic during The 2007 guidance took into account the results of a 2006 spring 2009, were considered acceptable and feasible for most opinion poll conducted with a representative national sample of parents and caregivers, even when parents had to miss work 1,697 adults aged ≥18 years. The results indicated that when faced and in the absence of free or reduced-cost school lunches for with an outbreak of pandemic influenza, the majority of persons students (28,38–41). Other interventions that reduced the in the United States would be willing to make major changes in spread of H1N1pdm09 virus in some communities included their lives and cooperate with public health recommendations hand hygiene (42), regularly scheduled school summer breaks on the use of NPIs (http://archive.sph.harvard.edu/press- (19), and social distancing measures, such as cancelling mass releases/2006-releases/press10262006.html). Findings were gatherings and closing public places (22). US Department of Health and Human Services/Centers for Disease Control and Prevention MMWR / April 21, 2017 / Vol. 66 / No. 1 7

Recommendations and Reports BOX 2. Principles of community engagement Planning Implementation Before initiating a community engagement effort, For engagement to succeed, consider the following: consider the following: 5. Partnering with the community is necessary to create 1. Be clear about the purpose or goals of the engagement change and improve health. effort and the relevant populations and communities. 6. All aspects of community engagement must recognize 2. Become knowledgeable about the community’s culture, and respect the diversity of the community. Awareness economic conditions, social networks, political and of the various cultures of a community and other power structures, norms and values, demographic factors affecting diversity must be paramount in trends, history, and experience with efforts by outside planning, designing, and implementing approaches groups to engage it in various programs. Learn about to engaging a community. the community’s perceptions of those initiating the 7. Community engagement can only be sustained by engagement activities. identifying and mobilizing community assets and Initiation strengths and by developing the community’s capacity For engagement to occur, the following steps are and resources to make decisions and take action. necessary: 8. Organizations that would like to involve a community 3. Go to the community, establish relationships, build trust, and those seeking to effect change must be prepared work with the formal and informal leaders, and seek to release control of actions or interventions to the commitment from community organizations and community and be flexible enough to meet changing leaders to create processes for mobilizing the community. needs. 4. Remember and accept that collective self- 9. Community collaboration requires long-term determination is the responsibility and right of all commitment by the engaging organizations and people in a community. No external entity should its partners. assume the ability to bestow on a community the power to act in its own self-interest. Source: Adapted from: Agency for Toxic Substances and Disease Registry. Principles of community engagement. Atlanta, GA: CDC, Agency for Toxic Substances and Disease Registry. https://www.atsdr.cdc.gov/communityengagement/pdf/PCE_Report_Chapter_2_SHEF.pdf similar in a follow-up study during the 2009–2010 H1N1 information about pandemic influenza and NPI community pandemic (Box 1) (https://www.hsph.harvard.edu/horp/ engagement is available (supplementary Chapter 1 https://stacks. project-on-the-public-response-to-h1n1). cdc.gov/view/cdc/44313). For example, in 2006, 85% of the respondents said that they and all members of their household would stay home for 7–10 days if New Tools for Prepandemic Planning and another household member were ill with pandemic influenza. The Pandemic Assessment H1N1 opinion polls also identified barriers to implementation of NPIs among persons and communities (e.g., the ability to stay Novel Influenza Virus Pandemic Intervals home when ill, job security, and income protection) (https://www. hsph.harvard.edu/horp/project-on-the-public-response-to-h1n1). In 2014, CDC updated its 2008 guidance on pandemic States and localities could establish local planning councils or hold intervals to include six intervals that describe influenza public engagement meetings that address these and other issues pandemic progression in a way that supports flexible related to public health preparedness, pandemic education, and prepandemic preparedness and response. The intervals include planning. States and local communities also can draw on planning 1) investigation of novel influenza cases, 2) recognition of guidance provided in the CDC Public Health Preparedness potential for ongoing transmission, 3) initiation, 4) acceleration, Capabilities: National Standards for State and Local Planning, 5) deceleration of the pandemic wave, and 6) preparation for a which lists NPIs as one of 15 capabilities (https://www.cdc. future pandemic wave (43). These intervals can be used during gov/phpr/capabilities/DSLR_capabilities_July.pdf). Additional prepandemic planning and can serve as a platform for public health decision-making and actions during the beginning of 8 MMWR / April 21, 2017 / Vol. 66 / No. 1 US Department of Health and Human Services/Centers for Disease Control and Prevention

Recommendations and Reports a potential influenza pandemic. Each interval is associated When a pandemic begins, in the United States or with particular response activities, including implementation anywhere in the world, CDC makes an initial assessment of select NPIs during the initiation and acceleration intervals of viral transmissibility and clinical severity on the basis of and coordinated discontinuation of select community-level these multiple PSAF measures (Table 5) (44). On the basis NPIs reserved for pandemics during the deceleration interval of the initial assessment, CDC recommends that affected (Figure 2) (Table 4). Although the six-interval framework U.S. jurisdictions respond (and other jurisdictions prepare describes the sequence of pandemic disease evolution over to respond). Although data are limited during the initial time, the framework does not characterize the transmissibility 3–4 weeks after the emergence of a pandemic virus, these of the virus or the clinical severity of the outbreak. Therefore, early data are compiled into a broad, preliminary assessment. CDC has developed additional tools for pandemic planning CDC uses PSAF scores of viral transmissibility and clinical and response, including the Influenza Risk Assessment Tool severity to place the pandemic within one of four assessment (supplementary Chapter 2 https://stacks.cdc.gov/view/ quadrants (Figure 3). Depending on the surveillance capacity cdc/44313); https://www.cdc.gov/flu/pandemic-resources/ in the location where the novel virus emerges and first spreads, tools/risk-assessment.htm) and the Pandemic Severity 4–8 weeks or longer might be required to accrue sufficient data Assessment Framework (PSAF). Additional information about for a refined assessment of an evolving pandemic. Once data the pandemic intervals is available (supplementary Chapter 2 are available, the refined assessment is used to more precisely https://stacks.cdc.gov/view/cdc/44313). characterize the clinical severity and transmissibility of the Pandemic Severity Assessment Framework pandemic virus (Figure 4) (Table 6). These initial and refined assessments of pandemic severity are used, in coordination An influenza pandemic can range from mild to extremely with state and local public health partners, to guide the use severe in terms of clinical severity and transmission rate. of NPI measures. Additional information about PSAF is When a pandemic emerges, public health authorities should available (supplementary Chapter 2 https://stacks.cdc.gov/ assess its projected impact and recommend rapid action to view/cdc/44313). reduce virus transmission, protect populations at high risk for complications, and minimize societal disruption. As observed during the 2009 H1N1 pandemic response, attack Methods rates and case-fatality ratios can be difficult to measure early in a pandemic because of variations in care-seeking behavior Guidelines Development Process and testing practices; not everyone seeks care for their This 2017 update consists of three separate documents: this illness, and not everyone is tested and receives a diagnosis of report and two supplementary documents (https://stacks.cdc.gov/ pandemic influenza. As a result, severe cases might be more view/cdc/44313 and https://stacks.cdc.gov/view/cdc/44314). This likely to be reported, resulting in an overestimate of the case- report provides a brief introduction to pandemic influenza and hospitalization or case-fatality ratio. Tools for prepandemic NPIs; describes the 2007 strategy and the purpose of the updates, planning have been updated and augmented based on particularly after the 2009 H1N1 pandemic; outlines the methods that experience, and the Pandemic Severity Index in the used to develop this update and describe the evidence considered 2007 guidance has been replaced with PSAF. PSAF uses for NPI use during an influenza pandemic; presents CDC’s multiple clinical and epidemiologic indicators to provide NPI recommendations; and discusses key areas for further NPI a more comprehensive assessment of the transmissibility research. The two supplementary documents contain more specific and clinical severity of an emerging pandemic. Whereas and detailed information about pandemic influenza and NPIs. the Pandemic Severity Index was based on the assumption One document (Technical Report 1 https://stacks.cdc.gov/view/ that a future pandemic would cause an illness rate of 30% cdc/44313) is divided into chapters and provides an introduction in the U.S. population and relied on an assessment of case- to and overview of NPIs, a description of the new tools developed fatality ratios to determine severity of an evolving pandemic, for pandemic influenza planning and assessment, and a toolbox PSAF incorporates multiple measures of clinical severity describing the NPI evidence base, implementation issues, and (e.g., case-fatality ratios, case-hospitalization ratios, and research gaps. The second document (Technical Report 2 https:// deaths-hospitalizations ratios) and viral transmissibility stacks.cdc.gov/view/cdc/44314) consists of several appendices that (e.g., secondary household attack rates, school attack provide a glossary of terms, a detailed description of the methods rates, workplace attack rates, community attack rates, or used for developing the NPI recommendations, a comprehensive all of these, as well as rates of emergency department and summary table of the NPI body of evidence, and a list of tools outpatient visits for ILI) (44). and resources for pandemic influenza planning and preparedness. US Department of Health and Human Services/Centers for Disease Control and Prevention MMWR / April 21, 2017 / Vol. 66 / No. 1 9

Recommendations and Reports FIGURE 2. Preparedness and response framework for novel influenza A virus pandemics, with CDC intervals and World Health Organization phases Interpandemic Alert Pandemic Transition phase phase phase phase WHO Preparedness Response Recovery phases ( Risk assessment ) ypothetical number of influenza cases H CDC Investigation Recognition Initiation Acceleration Deceleration Preparation intervals Prepandemic intervals Pandemic intervals Influenza Risk Assessment Tool Pandemic Severity Assessment Framework Prepandemic planning scenarios Source: Adapted from: Holloway R, Rasmussen SA, Zaza S, Cox NJ, Jernigan DB; Influenza Pandemic Framework Workgroup. Updated preparedness and response framework for influenza pandemics. MMWR Recomm Rep 2014;63(No. RR-6). This 2017 update was developed through collaboration Use of NPIs During Influenza Pandemics involving input from several sources, including peer-reviewed Ten years ago, when the 2007 strategy was being developed, scientific literature, current research, CDC subject-matter the evidence for the use of NPIs during influenza pandemics experts, and external stakeholders (e.g., federal agencies, was limited, consisting primarily of historical analyses and public health officials, and business and education partners). contemporary observations rather than controlled scientific Development of these updated guidelines involved participation studies (45,46). These analyses and observations were by multiple CDC groups (e.g., the Community Mitigation supplemented by modeling studies that used historical data Guidelines Work Group and the coordination, abstraction, and to evaluate NPI use in U.S. cities during the 1918 pandemic consultation teams), as well as a group of external stakeholders (47,48) or that simulated pandemic scenarios as they might who reviewed a document, summarizing the overall direction occur in the future (49–51). The simulations, like the and key principles and concepts of the guidelines. Input historical analyses, generally supported the effectiveness from the work group members, subject-matter experts, and of early, targeted, and phased-in (layered) use of multiple stakeholders was considered and incorporated during the NPIs§ in preventing spread of disease, especially when used creation of the 2017 planning guidelines. The guidelines were developed during October 2011–October 2016 (Table 7). The § The pandemic mitigation framework proposed in the 2007 strategy was based complete list of contributors and their roles in the process are on the early, targeted, and layered use of multiple NPIs. NPIs should be initiated available (supplementary Appendix 2 https://stacks.cdc.gov/ early in a pandemic before local epidemics grow exponentially, be targeted toward those at the nexus of transmission (in affected areas where the novel view/cdc/44314). virus circulates), and be layered together to reduce community transmission as much as possible. A list of NPIs that are recommended at all times and those that are reserved for pandemics is provided (Table 1). 10 MMWR / April 21, 2017 / Vol. 66 / No. 1 US Department of Health and Human Services/Centers for Disease Control and Prevention

Recommendations and Reports in combination with antiviral medications (46,49). This Recommendations on the Use of conclusion seemed plausible, confirming the presumption Personal, Community, and that individual, partially effective NPIs act in complementary ways to decrease various factors that facilitate the spread Environmental NPIs of influenza under different circumstances and settings NPIs routinely recommended for prevention of respiratory (52). However, the NPI modeling studies had substantial virus transmission, such as seasonal influenza, include limitations, including lack of data supporting assumptions personal protective measures for everyday use (i.e., voluntary about the effectiveness of individual NPIs, economic and home isolation of ill persons, respiratory etiquette, and hand social costs of NPIs, and likely rates of compliance (46,49,53). hygiene) and environmental surface cleaning measures (i.e., In 2016, the evidence supporting the effectiveness of routine cleaning of frequently touched surfaces and objects). NPIs, both when used alone and in combination, was During an influenza pandemic, these NPIs are recommended more substantial and included controlled studies evaluating regardless of the pandemic severity level. Additional personal different NPIs. New modeling studies based on data and community NPIs also might be recommended. Personal collected during the 2009 H1N1 pandemic response also protective measures reserved for pandemics include voluntary became available. This update is based on approximately home quarantine of exposed household members and use of face 191 journal articles written in English and published from masks in community settings when ill. Community NPIs might 1990 through September 2016 that focused on personal include temporary closures or dismissals of child care facilities protective measures in general; school closure effectiveness and schools with students in grades kindergarten through 12 and unintended consequences; school absenteeism; spread (K–12), as well as other social distancing measures that increase of disease in child care facilities, colleges, and universities; the physical space between people (e.g., workplace measures impact of mass gatherings; and role and impact of NPIs such as replacing in-person meetings with teleconferences or in non–health care workplace settings. These articles were modifying, postponing, or cancelling mass gatherings) (Figure 5) reviewed, abstracted, and synthesized. To assess the strength (Table 1). Local decisions about NPI selection and timing involve of the evidence, a five-step NPI rating scheme process was consideration of overall pandemic severity and local conditions developed by adapting and applying the approach of the (1) and require flexibility and possible modifications as the Guide to Community Preventive Services (The Community pandemic progresses and new information becomes available. Guide) (https://www.thecommunityguide.org). Additional Updated recommendations on the use of NPIs to help slow information about the NPI rating scheme process is available the spread and decrease the impact of an influenza pandemic (supplementary Appendices 3 and 4 https://stacks.cdc.gov/ are provided, as is information on the rationale for using each view/cdc/44314). NPI as part of a comprehensive public health strategy for The selected articles were organized into three groups: pandemic response and the appropriate settings and use for 1) personal NPIs (personal protective measures for everyday ¶ each NPI according to the severity of the pandemic (Table 9). use and personal protective measures reserved for influenza The recommendations that follow are considered an update to pandemics); 2) community NPIs (social distancing measures the existing recommendations in the 2007 guidance because and school closures and dismissals); and 3) environmental the same set of NPIs has been maintained and recommended NPIs (surface cleaning measures) (Table 8). Key steps for use early in a pandemic. However, the difference between included selecting the relevant literature, abstracting and the guidance issued in 2007 and in 2017 is the clear delineation synthesizing the evidence, and assessing the evidence quality of NPIs into two categories: 1) NPIs recommended at all times (both individual study quality and quality of the body of and 2) NPIs recommended for use only during pandemics evidence). A recommendation was formulated based on (based on the level of pandemic severity and local conditions). the evidence of effectiveness for each NPI. The strength The 2017 update also provides additional evidence to support of NPI recommendations took into consideration the the NPI recommendations. effectiveness of the intervention, the ease of implementation ¶ (including unwanted consequences), and the importance Influenza pandemics can range from mild to extreme in terms of rates of viral of the intervention as a public health strategy. Additional transmission and clinical severity, as described in the four prepandemic planning information about the NPI evidence base is available scenarios developed by CDC. A very severe or extreme pandemic, such as the 1918 pandemic, is characterized by high to very high transmissibility and clinical (supplementary Chapter 3 https://stacks.cdc.gov/view/ severity. A severe pandemic, such as the pandemics of 1957 and 1968, is cdc/44313 and supplementary Appendix 5 https://stacks. characterized by high transmissibility and low to medium clinical severity. A mild or moderate pandemic, such as the 2009 pandemic, is characterized by cdc.gov/view/cdc/44314). low to medium transmissibility and clinical severity. US Department of Health and Human Services/Centers for Disease Control and Prevention MMWR / April 21, 2017 / Vol. 66 / No. 1 11

Recommendations and Reports Personal NPIS FIGURE 3. Pandemic Severity Assessment Framework for the initial assessment of the potential impact of an influenza pandemic NPIs that can be implemented by individual persons include High the following: y • Personal protective measures for everyday use: These include voluntary home isolation of ill persons, respiratory B D etiquette, and hand hygiene. • Personal protective measures reserved for pandemics: ansmissiblit These include voluntary home quarantine of exposed Moderate household members and use of face masks in community e of tr settings when ill. Personal Protective Measures for Everyday Use A C caled measur Personal protective measures are preventive actions that can S be used daily to slow the spread of respiratory viruses (https:// Low www.cdc.gov/nonpharmaceutical-interventions/personal/ Low Moderate High index.html; supplementary Chapter 3 https://stacks.cdc.gov/ Scaled measure of clinical severity view/cdc/44313). These measures include the following: Source: Reed C, Biggerstaff M, Finelli L, et al. Novel framework for assessing • Voluntary home isolation (i.e., staying home when epidemiologic effects of influenza epidemics and pandemics. Emerg Infect Dis 2013;19:85–91. ill or self-isolation): Persons with influenza stay home for at least 24 hours after a fever or signs of a fever Rationale for use as a public health strategy. Most (chills, sweating, and feeling warm or flushed)** are persons infected with an influenza virus might become gone (https://www.cdc.gov/flu/protect/preventing. infectious 1 day before the onset of symptoms and remain †† htm), except to obtain medical care or other necessities. infectious up to 5–7 days after becoming ill (54,55). However, To ensure that the fever is gone, patients’ temperature studies found that infants and immunocompromised should be measured in the absence of medication that persons might shed influenza viruses for prolonged periods lowers fever (e.g., acetaminophen or ibuprofen). In (up to 21 days and a mean of 19 days, respectively) addition to fever, common influenza symptoms include (56,57). The effectiveness of personal protective measures cough or chest discomfort, muscle or body aches, depends on their ability to interrupt virus transmission headache, and fatigue. Persons also might experience from one person to another. Voluntary home isolation, sneezing, a runny or stuffy nose, sore throat, vomiting, which is a form of patient isolation, prevents an ill person and diarrhea (https://www.cdc.gov/flu/consumer/ §§ from infecting other people outside of their household. symptoms.htm). Respiratory etiquette reduces the dispersion of droplets • Respiratory etiquette: Persons cover coughs and sneezes, contaminated with influenza virus being propelled through preferably with a tissue, and then dispose of tissues and the air by coughing or sneezing. Hand hygiene reduces disinfect hands immediately after a cough or sneeze, or (if the transmission of influenza viruses that occurs when one a tissue is not available) cough or sneeze into a shirt sleeve. person touches another (e.g., with a contaminated hand). Touching the eyes, nose, and mouth should be avoided to Contamination also can occur through self-inoculation via help slow the spread of germs (https://www.cdc.gov/flu/ fomite transmission (indirect contact transmission) when protect/covercough.htm). persons touch a contaminated surface and then touch • Hand hygiene: Persons perform regular and thorough their nose with a contaminated hand. A study conducted hand washing with soap and water (or use alcohol-based in households in Bangkok, Thailand, found that increased hand sanitizers containing at least 60% ethanol or handwashing reduced surface contamination with influenza isopropanol when soap and water are not available). virus, which lowered the potential for self-inoculation via fomite transmission (58). Additional studies found that ** Although many authorities use either 100°F or 100.4°F (37.8°C) as indicative influenza viruses can remain viable on the human hand for of fever, this number can vary depending on factors such as the method of measurement and the age of the person. Therefore, other values for fever could roughly 3–5 minutes (59) and that influenza viruses can be appropriate. CDC has public health recommendations that are based on remain on fingers for 30 minutes after contamination (60). the presence (or absence) of fever (i.e., persons’ temperature is not higher than their own normal temperature). §§ †† Additional information about isolation and quarantine is available at https:// Guidance for caring for persons at home who have influenza symptoms is www.cdc.gov/quarantine/QuarantineIsolation.html. available at https://www.cdc.gov/flu/consumer/caring-for-someone.htm. 12 MMWR / April 21, 2017 / Vol. 66 / No. 1 US Department of Health and Human Services/Centers for Disease Control and Prevention

Recommendations and Reports FIGURE 4. Pandemic Severity Assessment Framework using surveillance indicators for the refined assessment* of an influenza pandemic on the basis of past pandemics and influenza seasons 5 1918 4 1968 1957 y ansmissibilit e of tr3 2009 caled measur S 2 1977–78 2007–08 1 2006–07 1 2 3 4 5 6 7 Scaled measure of clinical severity Source: Adapted from: Reed C, Biggerstaff M, Finelli L, et al. Novel framework for assessing epidemiologic effects of influenza epidemics and pandemics. Emerg Infect Dis 2013;19:85–91. * Colors transition from light to dark as the estimated number of deaths increases. Transmissibility: measured on a scale of 1–5 and includes school, workplace, and community attack rates, secondary household attack rates, school and/or workplace absenteeism rates, and rates of emergency department and outpatient visits for influenza-like illness. Clinical severity: measured on a scale of 1–7 and includes case-fatality ratios, case-hospitalization ratios, and deaths-hospitalizations ratios. Settings and use. Voluntary home isolation involves for ill persons who lack paid sick leave or skin irritations persons remaining at home when ill with influenza. due to frequent hand washing). Respiratory etiquette and hand hygiene are recommended in homes and in all other community settings, including CDC recommendations schools and workplaces. All three personal protective Voluntary home isolation: CDC recommends voluntary home isolation of ill persons (staying home when ill) year-round and especially during measures are considered everyday preventive actions that annual influenza seasons and influenza pandemics. should be implemented year-round but that are especially Respiratory etiquette and hand hygiene: CDC recommends respiratory etiquette and hand hygiene in all community settings, including homes, important during annual influenza seasons and influenza child care facilities, schools, workplaces, and other places where people pandemics (Table 10). Use of these personal protective gather, year-round and especially during annual influenza seasons and measures might result in some secondary (unintended or influenza pandemics. unwanted) consequences (e.g., concerns about job security US Department of Health and Human Services/Centers for Disease Control and Prevention MMWR / April 21, 2017 / Vol. 66 / No. 1 13

Recommendations and Reports Personal Protective Measures Reserved for of the 1918 pandemic, and mathematical modeling studies Pandemics (supplementary Chapter 3 https://stacks.cdc.gov/view/cdc/44313 Voluntary home isolation, respiratory etiquette, and hand and supplementary Appendix 5 https://stacks.cdc.gov/view/ hygiene are recommended during both annual influenza cdc/44314). seasons and influenza pandemics. Additional personal protective Settings and use. Voluntary home quarantine of exposed measures that might be recommended during pandemics include household members might be recommended during severe, voluntary home quarantine of exposed household members and very severe, or extreme influenza pandemics (Table 10) the use of face masks in community settings when ill. These to help reduce the chance of transmitting the virus to measures might contribute to reductions in transmission of others outside of the household. Advance planning is pandemic influenza viruses when the level of pandemic severity needed to minimize potential secondary consequences and local conditions warrant their use (supplementary Chapter 3 for persons who have special cultural, economic, legal, https://stacks.cdc.gov/view/cdc/44313). mental, physical, or social status needs (e.g., older adults who depend on necessary community-based services such Voluntary Home Quarantine as home-delivered meals and transportation to health Voluntary home quarantine of non-ill household members of care services). Other secondary consequences might persons with influenza (also called self-quarantine or household include missed work and loss of income for persons whose quarantine) helps prevent disease spread from households employers do not have paid sick leave policies that include to schools, workplaces, and other households because those home quarantine during pandemics. household members have been exposed to the influenza virus. CDC recommendations Exposed household members of symptomatic persons (with Voluntary home quarantine: CDC might recommend voluntary home confirmed or probable pandemic influenza) should stay home quarantine of exposed household members as a personal protective for up to 3 days (the estimated incubation period for seasonal measure during severe, very severe, or extreme influenza pandemics in influenza) (61) starting from their initial contact with the ill combination with other personal protective measures such as respiratory etiquette and hand hygiene. If a member of the household is symptomatic person. If they then become ill, they should practice voluntary with confirmed or probable pandemic influenza, then all members of the home isolation (i.e., they should remain at home until recovered household should stay home for up to 3 days (the estimated incubation period for seasonal influenza),¶¶ starting from their initial contact with the as discussed previously; https://www.cdc.gov/quarantine/ ill person, to monitor for influenza symptoms. index.html). For certain exposed household members (e.g., those at high risk for influenza complications or with severe Use of Face Masks in Community Settings immune deficiencies), guidelines should be consulted regarding the prophylactic use of antiviral medications (https://www.cdc. Face masks (disposable surgical, medical, or dental procedure gov/flu/professionals/antivirals/index.htm). masks) are widely used by health care workers to prevent Rationale for use as a public health strategy. Voluntary respiratory infections both in health care workers and patients. home quarantine might help slow a pandemic by reducing They also might be worn by ill persons during severe, very community transmission from households with a person who severe, or extreme pandemics to prevent spread of influenza to has influenza because the exposed household members are at household members and others in the community. However, increased risk for infection. Furthermore, certain infected (but little evidence supports the use of face masks by well persons not yet symptomatic) household members could begin shedding in community settings, although some trials conducted during influenza virus at least a day before exhibiting symptoms and the 2009 H1N1 pandemic found that early combined use of could infect friends, neighbors, and others in the community face masks and other NPIs (such as hand hygiene) might be (e.g., at school or work) before becoming symptomatic. Therefore, effective (supplementary Chapter 3 https://stacks.cdc.gov/ all members of a household with a symptomatic person (with view/cdc/44313). confirmed or probable pandemic influenza) might be asked to Rationale for use as a public health strategy. Face masks stay home for a specified period of time (up to 3 days) to assess for provide a physical barrier that prevents the transmission early signs and symptoms of pandemic influenza virus infection. If of influenza viruses from an ill person to a well person by other household members become ill during this period, then the blocking large-particle respiratory droplets propelled by time for voluntary home quarantine might need to be extended coughing or sneezing. Face mask use by well persons is not for another incubation period. The evidence for voluntary home routinely needed in most situations to prevent acquiring the quarantine, particularly when used in combination with other influenza virus. However, use of face masks by well persons NPIs, includes a systematic literature review, historical analyses ¶¶ If the incubation period for the next pandemic were shorter or longer than 3 days, CDC would amend the recommendation accordingly. 14 MMWR / April 21, 2017 / Vol. 66 / No. 1 US Department of Health and Human Services/Centers for Disease Control and Prevention

Recommendations and Reports FIGURE 5. Phased addition of nonpharmaceutical interventions to prevent the spread of pandemic influenza in communities Seasonal or novel Severity and influenza virus transmissibility Recommended NPIs Expected outcomes All levels of seasonal NPIs that are recommended at all times Seasonal influenza severity Personal and transmissibility • Voluntary home isolation (staying home when ill) • Respiratory etiquette (covering coughs and sneezes) • Hand hygiene (washing hands with soap and water or use of alcohol- based hand sanitizer when soap and water are not available) Environmental • Routine surface cleaning of frequently touched surfaces and objects • Reduced spread of (e.g., tables, door knobs, toys, desks, and computer keyboards) infectious disease • Reduced load for health care facilities • Low to medium NPIs that might be added during a pandemic • Reduced morbidity severity and Personal and mortality transmissibility • Voluntary home quarantine (household members of ill persons stay Novel • High transmissibility home for up to 3 days and then remain home if they become ill) (potential and low to medium • Face mask use by ill persons for source control pandemic) severity Community • High to very high • School closures and dismissals transmissibility and • Mass gathering modifications/postponements/cancellations severity • Other social distancing measures (e.g., offering telecommuting in workplaces or seating students further apart in classrooms) Abbreviation: NPI = nonpharmaceutical intervention. might be beneficial in certain situations (e.g., when persons CDC recommendations at high risk for influenza complications cannot avoid crowded Use of face masks by ill persons: CDC might recommend the use of settings or parents are caring for ill children at home). Face face masks by ill persons as a source control measure during severe, mask use by well persons also might reduce self-inoculation very severe, or extreme influenza pandemics when crowded community settings cannot be avoided (e.g., when adults and children with influenza (e.g., touching the nose with the hand after touching a symptoms seek medical attention) or when ill persons are in close contact contaminated surface). with others (e.g., when symptomatic persons share common spaces with Settings and use. Disposable surgical, medical, and dental other household members or symptomatic postpartum women care for and nurse their infants). Some evidence indicates that face mask use by procedure masks are used widely in health care settings ill persons might protect others from infection. to prevent exposure to respiratory infections. Face masks Use of face masks by well persons: CDC does not routinely recommend the use of face masks by well persons in the home or other community have few secondary consequences (e.g., discomfort or settings as a means of avoiding infection during influenza pandemics difficulty breathing) when worn properly and consistently, except under special, high-risk circumstances (https://www.cdc.gov/flu/ professionals/infectioncontrol/maskguidance.htm). For example, during and face masks sized for children are available. (Additional a severe pandemic, pregnant women and other persons at high risk for information about face masks is available at https://www. influenza complications might use face masks if unable to avoid crowded settings, especially if no pandemic vaccine is available. In addition, persons fda.gov/medicaldevices/productsandmedicalprocedures/ caring for ill family members at home (e.g., a parent of a child exhibiting generalhospitaldevicesandsupplies/personalprotectiveequipment/ influenza symptoms) might use face masks to avoid infection when in ucm055977.htm and https://www.osha.gov/Publications/ close contact with a patient, just as health care personnel wear masks in health care settings. respirators-vs-surgicalmasks-factsheet.html.) US Department of Health and Human Services/Centers for Disease Control and Prevention MMWR / April 21, 2017 / Vol. 66 / No. 1 15

Recommendations and Reports Community NPIs of a pandemic, before many students and staff members become NPIs that can be implemented by communities include the ill. Preemptive, coordinated dismissals can be implemented by following: the following facilities for the following reasons: • School closures and dismissals: These include temporary • Child care facilities and K–12 schools closures and dismissals of child care facilities, K–12 – Children have higher influenza attack rates than adults (62) schools, and institutions of higher education. and are infectious for a longer period than adults (63,64). • Social distancing measures: These include measures for – Influenza transmission is common in schools and schools, workplaces, and mass gatherings. contributes to school absenteeism and parental absenteeism from work (65,66). School Closures and Dismissals – The presence of school-aged children in a household is In the event of a pandemic, state and local public health authorities a risk factor for influenza virus infection in families play an important role in protecting the school community and (62,65,67). should establish and maintain partnerships with district and school – Social contact and mixing patterns among school-aged leaders, school emergency operations planning teams, and local children differ substantially depending on the grade municipality leaders (e.g., mayors). Public health authorities are a and school level, during various periods of the school credible source of information, have multiple (often free) resources day, between weekdays and weekends, and between available for information awareness campaigns, and provide regular school terms and holiday breaks (68–71). guidance for increasing school response measures. Depending on Physical floor plans and intergrade activities (e.g., the severity of the pandemic, these measures might range from cafeteria size and lunch breaks) also can affect in-school everyday preventive actions to preemptive, coordinated school social mixing (68). closures and dismissals. A school closure means closing a school and – Schoolchildren can introduce the influenza virus into sending all the students and staff members home, whereas during a community, leading to increased rates of illness among a school dismissal, a school might stay open for staff members their household or community contacts (72–74). while the children stay home. Preemptive school dismissals can • Institutions of higher education be used to disrupt transmission of influenza before many students – Influenza outbreaks on college and university campuses and staff members become ill. Coordinated dismissals refer to the typically have high attack rates (44%–73%) (75–78) simultaneous or sequential closing of schools in a jurisdiction. Thus, and cause substantial morbidity (79,80). For example, preemptive, coordinated school closures and dismissals can be used during the 2009 H1N1 pandemic, influenza spread early during an influenza pandemic to prevent virus transmission rapidly through a university campus within 2 weeks in schools and surrounding communities by reducing close contact (81); on another residential campus, one infected among the following groups (supplementary Chapter 3 https:// freshman initiated an outbreak that resulted in 226 stacks.cdc.gov/view/cdc/44313): laboratory-confirmed cases. Freshmen were the main • Children in child care centers and preschools facilitators of the spread of the H1N1pdm09 virus • School-aged children and teens in K–12 schools because of their higher number and frequency of social • Young adults in institutions of higher education contacts (82). During a dismissal, the school facilities are kept open, which – Influenza is more prevalent among residential students allows teachers to develop and deliver lessons and materials, thus at boarding schools and colleges than among maintaining continuity of teaching and learning, and allows nonresidential students (78,83). other staff members to continue to provide services and help with – ILIs are common among college and university students additional response efforts. School closures and dismissals might and are associated with increased health care use, be coupled with social distancing measures (e.g., cancelling decreased health status, and impaired school sporting events and other mass gatherings) to reduce out-of- performance (84). school social contact among children when schools are closed. Implementation of preemptive, coordinated school Rationale for use as a public health strategy. Preventing the closures and dismissals during an evolving influenza spread of disease in educational settings among children and pandemic might have one or more of the following three young adults reduces the risk for infection for these age groups public health objectives***: and slows virus transmission in the community. Components *** Additional information on the use of preemptive, coordinated school closures of the strategy might include preemptive, coordinated school and dismissals of different durations is available (supplementary Chapter 3 closures and dismissals implemented during the earliest stages https://stacks.cdc.gov/view/cdc/44313). 16 MMWR / April 21, 2017 / Vol. 66 / No. 1 US Department of Health and Human Services/Centers for Disease Control and Prevention

Recommendations and Reports • Objective 1: To gain time for an initial assessment of not reduce ILI transmission in the rural community (86). transmissibility and clinical severity of the pandemic virus Similarly, closing 559 Michigan schools at least once in the very early stage of its circulation in humans (closures during the fall wave (i.e., second wave) of the 2009 H1N1 for up to 2 weeks) pandemic had little effect on community levels of ILI (87). • Objective 2: To slow down the spread of the pandemic For more information about preparing for influenza and virus in areas that are beginning to experience local the different types of dismissals, see CDC websites regarding outbreaks and thereby allow time for the local health care 1) child care facilities (https://www.cdc.gov/h1n1flu/childcare/ system to prepare additional resources for responding to toolkit/pdf/childcare_toolkit.pdf), 2) K–12 schools (https:// increased demand for health care services (closures up to www.cdc.gov/h1n1flu/schools/toolkit/pdf/schoolflutoolkit.pdf), 6 weeks) and 3) institutions of higher education (https://www.cdc.gov/ • Objective 3: To allow time for pandemic vaccine h1n1flu/institutions/toolkit/pdf/IHE_toolkit.pdf). production and distribution (closures up to 6 months) Settings and use. Preemptive, coordinated school closures Two other types of school closures and dismissals might and dismissals might be implemented at child care facilities, be implemented during a pandemic for public health or K–12 schools, and institutions of higher education. They are institutional reasons. These interventions do not slow disease most likely to be implemented when an influenza pandemic spread in the community; therefore, they are not considered is severe, very severe, or extreme (Table 10). Secondary NPIs. They include the following: consequences include missed work and loss of income for • Selective school closures and dismissals: These might parents who stay home from work to care for their children be implemented by schools that serve students at high risk and missed opportunities to vaccinate school-aged children ††† for complications from infection with influenza, rapidly unless other mechanisms are considered. especially when transmission rates are high. For example, a school that serves children with certain medical CDC recommendations conditions or pregnant teens might decide to close while School closures and dismissals: CDC might recommend the use of preemptive, coordinated school closures and dismissals during severe, other schools in the area remain open. In addition, some very severe, or extreme influenza pandemics. This recommendation is in communities or early childhood programs might consider accord with the conclusions of the U.S. Community Preventive Services Task Force (https://www.thecommunityguide.org/findings/emergency- closing child care facilities to help decrease the spread of preparedness-and-response-school-dismissals-reduce-transmission- influenza among children aged <5 years. Selective pandemic-influenza), which makes the following recommendations: dismissals are intended to protect persons at high risk for • The task force recommends preemptive, coordinated school dismissals during a severe influenza pandemic. influenza rather than to help reduce virus transmission • The task force found insufficient evidence to recommend for or within the community. against preemptive, coordinated school dismissals during a mild or moderate influenza pandemic. In these instances, jurisdictions should • Reactive school closures and dismissals: These might be make decisions that balance local benefits and potential harms. implemented when many students and staff members are ill and not attending school or when many students and Social Distancing Measures for Schools, staff members are arriving at school ill and being sent Workplaces, and Mass Gatherings home. For example, a child care center might close because it is unable to operate under these conditions. Reactive Social distancing measures can reduce virus transmission dismissals, which might occur during outbreaks of seasonal by decreasing the frequency and duration of social contact influenza (85) and during pandemics (15), are unlikely to among persons of all ages. These measures are common-sense affect virus transmission because they typically take place approaches to limiting face-to-face contact, which reduces after considerable, if not widespread, transmission has person-to-person transmission. already occurred in the community. For example, a 4-day Rationale for use as a public health strategy. Social reactive closure in a western Kentucky school district did distancing measures that reduce opportunities for person-to- person virus transmission can help delay the spread and slow ††† Persons at high risk for influenza-related complications include children aged the exponential growth of a pandemic. The optimal strategy is <5 years (and especially aged <2 years), adults aged ≥65 years, pregnant to implement these measures simultaneously in places where women, residents of nursing homes and other long-term care facilities, and American Indians/Alaska Natives. Those at high risk also include persons persons gather. Although direct evidence is limited for the with asthma, neurological and neurodevelopmental conditions, chronic lung effectiveness of these measures, components of the strategy disease, and heart disease; disorders of the blood, endocrine system, kidney, might include reducing social contacts at the following places: or liver; metabolic disorders; and weakened immune systems from disease or medication. Two other groups at higher risk are persons aged <19 years who • Schools: Children have higher influenza attack rates than receive long-term aspirin therapy and those with extreme obesity (https:// adults, and influenza transmission is common in schools. www.cdc.gov/flu/about/disease/high_risk.htm). US Department of Health and Human Services/Centers for Disease Control and Prevention MMWR / April 21, 2017 / Vol. 66 / No. 1 17

Recommendations and Reports • Workplaces: More than half of all U.S. adults participate might be implemented with few secondary consequences §§§ in the U.S workforce, and workers often share office (e.g., increased use of e-mail and teleconferences in some space and equipment and have frequent face-to-face workplaces), whereas others might require advance planning contact. Influenza attack rates in working-age adults (aged (e.g., modification of mass gatherings). Examples of practical 18–64 years) might be as high as 15.5% during a single measures that might reduce face-to-face contact in community influenza season (88). settings include the following: • Mass gatherings: Group events such as concerts, festivals, • If schools remain open during a pandemic, divide school and sporting events bring people into close contact for classes into smaller groups of students and rearrange desks extended periods (89–92). A systematic literature review so students are spaced at least 3 feet (98) from each other of respiratory disease outbreaks related to mass gatherings in a classroom. in the United States during 2005–2014 indicated that 40 • Offer telecommuting and replace in-person meetings in of 72 different outbreaks were associated with state or the workplace with video or telephone conferences. county agriculture fairs and (zoonotic) transmission of • Modify, postpone, or cancel mass gatherings. influenza A H3N2v, and 25 outbreaks were associated with residential youth summer camps and person-to- CDC recommendations person transmission of influenza A H1N1 (93). An Social distancing measures: Even though the evidence base for the effectiveness of some of these measures is limited, CDC might recommend infected traveler attending a mass gathering might the simultaneous use of multiple social distancing measures to help introduce influenza to a previously unaffected area, and a reduce the spread of influenza in community settings (e.g., schools, workplaces, and mass gatherings) during severe, very severe, or extreme person who becomes infected at the event can further influenza pandemics while minimizing the secondary consequences of the spread the infection after returning home (89,90,92,94–96). measures. Social distancing measures include the following: Even when a circulating virus has a relatively low basic • Increasing the distance to at least 3 feet (98) between persons when possible might reduce person-to person transmission. This applies reproductive rate (R ), intensely crowded settings might to apparently healthy persons without symptoms. In the event of a 0 very severe or extreme pandemic, this recommended minimal lead to high secondary attack rates (92). For example, distance between people might be increased. during the 2013 Hajj (Islamic pilgrimage to Mecca) in • Persons in community settings who show symptoms consistent with Saudi Arabia, influenza A/H1N1 virus was found in only influenza and who might be infected with (probable) pandemic influenza should be separated from well persons as soon as practical, two Indonesians on arrival but spread to 25 persons from be sent home, and practice voluntary home isolation. Africa, Central Asia, and Southeast Asia after the Hajj because of the extremely crowded conditions when performing rituals (97). Environmental NPIs: Environmental Multiple social distancing measures can be implemented Surface Cleaning Measures simultaneously. Although there is limited empirical evidence supporting the effectiveness of implementing any individual Environmental surface cleaning measures can help measure alone (other than school closures and dismissals), eliminate influenza viruses from frequently touched the evidence for implementing multiple social distancing surfaces and objects, including tables, door knobs, measures in combination with other NPIs includes systematic toys, desks, and computer keyboards. These measures literature reviews, historical analyses of the 1918 pandemic, involve cleaning surfaces with detergent-based cleaners and mathematical modeling studies (supplementary Chapter 3 or disinfectants that have been registered with the https://stacks.cdc.gov/view/cdc/44313 and supplementary Environmental Protection Agency.¶¶¶ Appendix 5 https://stacks.cdc.gov/view/cdc/44314). Rationale for use as a public health strategy. Although the Settings and use. Social distancing measures can be percentage of influenza cases involving contact transmission implemented in a range of community settings, including (i.e., hand transfer of virus from contaminated objects to the educational facilities, workplaces, and public places where eyes, nose, or mouth) is unknown, this mode of transmission is a people gather (e.g., parks, religious institutions, theaters, and recognized route of virus spread (99). The routine use of cleaning sports arenas). The choice of social distancing measure depends measures that eliminate viruses from contaminated surfaces on the severity of the pandemic (Table 10). Certain measures might reduce the spread of influenza viruses (supplementary Chapter 3 https://stacks.cdc.gov/view/cdc/44313). §§§ As of September 2016, the U.S. workforce included 62.9% of the civilian, noninstitutionalized population aged ≥16 years (Source: US Bureau of Labor ¶¶¶ Antimicrobial products registered for use against H1N1 influenza and other Statistics. The employment situation—September 2016. Washington, DC: influenza A viruses on hard surfaces (https://archive.epa.gov/pesticides/ US Department of Labor; 2016. https://www.bls.gov/news.release/archives/ oppad001/web/pdf/influenza-a-product-list.pdf). empsit_10072016.pdf). 18 MMWR / April 21, 2017 / Vol. 66 / No. 1 US Department of Health and Human Services/Centers for Disease Control and Prevention

Recommendations and Reports Settings and use. Environmental surface cleaning Although community-level NPIs can help slow virus measures are recommended for frequently touched transmission, as supported by historical information surfaces and objects in homes, child care facilities, schools, (100), empirical observations (101), and mathematical workplaces, and other places where persons gather. modeling (102), these measures are likely to cause unwanted These measures can be used for prevention of seasonal consequences by introducing new norms for social behavior influenza and in all pandemic severity scenarios (Table 10). (e.g., adopting precautionary health-protective behaviors Use of these measures might result in some secondary such as limiting face-to-face contact with family and friends, consequences (e.g., failing to read instruction labels only shopping for essential items, avoiding places where before applying disinfectants to ensure that they are safe people congregate, or not using public transportation) and appropriate to use or cleaning with poor ventilation (103), interrupting routine societal functions, and entailing during the application process). additional costs. If an evolving influenza pandemic is characterized by high clinical severity, the benefits of CDC recommendations deploying NPIs, including those with greater potential for Environmental surface cleaning measures: CDC recommends secondary consequences, are likely to outweigh potential environmental surface cleaning measures in all settings, including homes, schools, and workplaces, to remove influenza viruses from frequently touched harms. The more difficult decision is determining how surfaces and objects. Use of these measures might help prevent transmission and when to implement the community-level NPIs that of various infectious agents, including seasonal and pandemic influenza (https://www.cdc.gov/nonpharmaceutical-interventions/environmental/ are more disruptive to society (e.g., temporary K–12 index.html; https://www.cdc.gov/oralhealth/infectioncontrol/questions/ school closures) during pandemics of moderate severity. In cleaning-disinfecting-environmental-surfaces.html). each locality, the goal should be to implement NPIs early Additional guidance is available from CDC for health care facilities (https:// www.cdc.gov/hicpac/pdf/guidelines/eic_in_HCF_03.pdf), schools (https:// enough and long enough to maximize effectiveness while www.cdc.gov/flu/school/cleaning.htm), and airline, travel, and transportation minimizing economic and social costs to ensure that NPIs industries (https://www.cdc.gov/flu/pandemic-resources/archived/ transportation-planning.html). are commensurate to the pandemic severity. New Elements Added in 2017 Discussion New elements in this report, in addition to the evidence- This report expands the NPI guidance presented in the based NPI recommendations, include a summary of key lessons 2007 report by providing evidence-based recommendations learned from the 2009 H1N1 pandemic response (Box 1), on the use of the same set of NPIs. These NPIs include information on community engagement and preparedness personal protective measures for everyday use and for use (supplementary Chapter 1 https://stacks.cdc.gov/view/ during a pandemic, community measures (school closures and cdc/44313), and information on new or updated pandemic dismissals and social distancing), and environmental surface assessment tools (supplementary Chapter 2 https://stacks.cdc. cleaning measures. gov/view/cdc/44313), which include the novel influenza virus pandemic intervals tool, the Influenza Risk Assessment Tool, Key Concepts Maintained from and PSAF. As described in the following sections, this report also presents two additional planning tools designed to assist 2007 Guidance states and localities in ensuring pandemic preparedness. The rationale for and key concepts regarding the use of NPIs Prepandemic Planning Scenarios for NPI during influenza pandemics first presented in the 2007 guidance Implementation According to Pandemic Severity remain unchanged. Because production of a pandemic vaccine can take up to 6 months and antiviral medications might During the initial stages of a pandemic, CDC will use the be prioritized for treatment, NPIs are likely to be the only PSAF tool to prepare an initial assessment of pandemic severity prevention tools available early in a pandemic. Therefore, they that provides early guidance on use of NPIs to help slow the are critical to slowing the spread of the pandemic influenza virus transmission of the novel virus. To facilitate the use of the initial while a pandemic vaccine is under development. assessment information by state and local health departments, Like the 2007 strategy, this 2017 update affirms the CDC has provided a set of four prepandemic planning scenarios. importance of prepandemic planning and preparedness for Each scenario aligns with one of the four assessment quadrants use of NPIs during a pandemic response and recommends (Figure 3) and provides information on past influenza pandemics the early, targeted, and simultaneous implementation of for comparison (Table 9). These planning scenarios are designed multiple NPIs to decrease influenza virus transmission. to facilitate state and local prepandemic planning for NPI US Department of Health and Human Services/Centers for Disease Control and Prevention MMWR / April 21, 2017 / Vol. 66 / No. 1 19

Recommendations and Reports implementation according to pandemic severity (as classified by other workplaces. These guides have been updated, and two new PSAF) (Figure 6) (Tables 9 and 10). After sufficient epidemiologic guides have been developed for public health communicators data are accrued and the refined assessment of pandemic severity and event planners that address NPI communications and becomes available, CDC will issue updated pandemic NPI modification, postponement, or cancellation of mass gatherings. guidance, which will be tailored more precisely to the specific These guides are intended to help operationalize the 2017 update pandemic. Additional information about the planning scenarios and provide specific information that can assist different groups and phasing of NPIs is available (supplementary Chapter 2 https:// in their prepandemic planning and decision-making (https:// stacks.cdc.gov/view/cdc/44313). www.cdc.gov/nonpharmaceutical-interventions). Supplemental Prepandemic NPI Planning Guides Future Research The 2007 report included supplemental prepandemic NPI planning guides for individuals and families; child care Although progress has been made since 2009 toward building programs, K–12 schools, and institutions of higher education; the evidence base for use of NPIs to slow the spread of pandemic community- and faith-based organizations; and businesses and influenza, additional research is needed. For personal NPIs, FIGURE 6. U.S. Department of Health and Human Services pandemic planning scenarios based on the Pandemic Severity Assessment Framework Moderate High Very high 1918 5 pandemic severity severity severity 4 1968 1957 pandemic pandemic y ansmissibilit 2009 3 pandemic e of tr caled measur S 2 2014–15 Low severity 1 Seasonal 2011–12 range 1 2 3 4 5 6 7 Scaled measure of clinical severity Source: Adapted from: Reed C, Biggerstaff M, Finelli L, et al. Novel framework for assessing epidemiologic effects of influenza epidemics and pandemics. Emerg Infect Dis 2013;19:85–91. 20 MMWR / April 21, 2017 / Vol. 66 / No. 1 US Department of Health and Human Services/Centers for Disease Control and Prevention

Recommendations and Reports areas for additional research include evaluating the effects of (https://www.cdc.gov/flu/pandemic-resources/planning- increased frequency and quality of hand washing on influenza preparedness/community-mitigation.html). In addition, virus transmission, determining the role of infected persons who some community-level NPIs that potentially have the greatest are not symptomatic in the transmission of influenza viruses in epidemiologic effects on pandemic influenza virus transmission households, and assessing the effectiveness, acceptability, and in communities, most notably school closures and dismissals, feasibility of recommending face mask use by well persons in also are most likely to be associated with secondary (unwanted) community settings as a means of avoiding infection during a consequences (104). Hence, prepandemic planning, including pandemic. For community NPIs, one topic for additional study engaging communities in planning activities well ahead of the involves gathering empirical data on social mixing patterns in next pandemic, is critical to enable appropriate local decision- schools and community settings. These data can be used to making during the early stages of a pandemic. create high-fidelity, high-resolution mathematical models of After the 2009 H1N1 pandemic, evidence on the effectiveness virus transmission in these settings to facilitate data-driven and feasibility of NPIs expanded substantially. A summary of evaluations of different social distancing measures. Another the evidence in this 2017 update includes 2009 H1N1-related area of research for community NPIs involves assessing the research (supplementary Appendix 5 https://stacks.cdc.gov/view/ potential secondary consequences (e.g., missed work) of select cdc/44314). However, knowledge gaps remain and should be community-level measures (e.g., school closures) for families, addressed by future research. Further updates of these guidelines communities, and society to assess the economic effects of these will be developed and issued when significant new information measures. For environmental NPIs, additional research is needed and evidence emerges about the effectiveness and feasibility of to better understand surface contamination (e.g., which types NPIs in mitigating the impact of pandemic influenza. of surfaces are more likely to be contaminated with influenza viruses) and identify situations in which surface cleaning should References be emphasized (e.g., in households with confirmed influenza 1. Barrios LC, Koonin LM, Kohl KS, Cetron M. Selecting nonpharmaceutical cases versus in healthy households). Additional information strategies to minimize influenza spread: the 2009 influenza A (H1N1) pandemic and beyond. Public Health Rep 2012;127:565–71. https:// about NPI research gaps is available (supplementary Chapter 3 doi.org/10.1177/003335491212700606 https://stacks.cdc.gov/view/cdc/44313). 2. Monto AS, Webster RG. [Chapter 2]. In: Webster RG, Monto AS, Braciale TJ, Lamb RA, eds. Textbook of influenza. 2nd. West Sussex, UK: John Wiley and Sons, Ltd; 2013:20–33. 3. Shrestha SS, Swerdlow DL, Borse RH, et al. Estimating the burden Conclusion of 2009 pandemic influenza A (H1N1) in the United States (April 2009–April 2010). Clin Infect Dis 2011;52(Suppl 1):S75–82. The 2009 H1N1 pandemic provided an opportunity to test, https://doi.org/10.1093/cid/ciq012 in practice, the key concepts of NPIs in mitigating the impact 4. Jhung MA, Swerdlow D, Olsen SJ, et al. Epidemiology of 2009 of an influenza pandemic, just 2 years after the publication of pandemic influenza A (H1N1) in the United States. Clin Infect Dis the 2007 guidance. As the experience from 2009 has shown, 2011;52(Suppl 1):S13–26. https://doi.org/10.1093/cid/ciq008 5. CDC. Updated CDC estimates of 2009 H1N1 influenza cases, NPIs can be a critical component of pandemic influenza hospitalizations, and deaths in the United States, April 2009–April 10, mitigation. Although well-matched pandemic vaccines remain 2010. Atlanta, GA: US Department of Health and Human Services, the main tool in reducing the risk of acquiring infection and in CDC; 2010. https://www.cdc.gov/h1n1flu/estimates_2009_h1n1.htm 6. Labrosse B, Tourdjman M, Porcher R, et al. Detection of extensive cross- controlling the spread of a pandemic virus, vaccines might not neutralization between pandemic and seasonal A/H1N1 influenza viruses be widely available for up to 6 months after the emergence of using a pseudotype neutralization assay. PLoS One 2010;5:e11036. a pandemic influenza virus, given current vaccine production https://doi.org/10.1371/journal.pone.0011036 7. Nougairède A, Ninove L, Zandotti C, et al. Novel virus influenza A technology. Furthermore, as during the 2009 H1N1 pandemic, (H1N1sw) in South-Eastern France, April–August 2009. PLoS One antiviral medications might be prioritized for treatment but 2010;5:e9214. https://doi.org/10.1371/journal.pone.0009214 not used for widespread chemoprophylaxis because of concerns 8. CDC. Use of influenza A (H1N1) 2009 monovalent vaccine: about antiviral resistance and limited stockpiles of antiviral recommendations of the Advisory Committee on Immunization Practices (ACIP), 2009. MMWR Recomm Rep 2009;58(No. RR-10). medications. Therefore, NPIs might be the only prevention 9. Fell DB, Sprague AE, Liu N, et al; Better Outcomes Registry & Network tools readily available for persons and communities to help (BORN) Ontario. H1N1 influenza vaccination during pregnancy and slow transmission of an influenza virus during the initial fetal and neonatal outcomes. Am J Public Health 2012;102:e33–40. https://doi.org/10.2105/AJPH.2011.300606 stages of a pandemic. However, individual NPIs might be only 10. Richards JL, Hansen C, Bredfeldt C, et al. Neonatal outcomes after partially effective in limiting community transmission when antenatal influenza immunization during the 2009 H1N1 influenza implemented alone. Thus, the most efficient implementation pandemic: impact on preterm birth, birth weight, and small for gestational age birth. Clin Infect Dis 2013;56:1216–22. https://doi. involves early, targeted, and layered use of multiple NPIs org/10.1093/cid/cit045 US Department of Health and Human Services/Centers for Disease Control and Prevention MMWR / April 21, 2017 / Vol. 66 / No. 1 21

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Recommendations and Reports CDC Community Mitigation Guidelines Work Group Alexandra Levitt, PhD, Office of Infectious Diseases, CDC, Stephanie Dopson, ScD, Influenza Coordination Unit, Office of Infectious Diseases, CDC, Mark Frank, MPH, Influenza Coordination Unit, Office of Infectious Diseases, CDC, Rachel Holloway, Influenza Coordination Unit, Office of Infectious Diseases, CDC, Lisa Koonin, DrPH, Influenza Coordination Unit, Office of Infectious Diseases, CDC, Sonja Rasmussen, MD, Influenza Coordination Unit, Office of Infectious Diseases, CDC, Stephen Redd, MD, Influenza Coordination Unit, Office of Infectious Diseases, CDC, Christopher de la Motte Hurst, MPH, Division of Global Migration and Quarantine, National Center for Emerging and Zoonotic Infectious Diseases, CDC, Neha Kanade, MPH, Division of Global Migration and Quarantine, National Center for Emerging and Zoonotic Infectious Diseases, CDC, Noreen Qualls, DrPH, Division of Global Migration and Quarantine, National Center for Emerging and Zoonotic Infectious Diseases, CDC, Jeanette Rainey, PhD, Division of Global Migration and Quarantine, National Center for Emerging and Zoonotic Infectious Diseases, CDC, Amra Uzicanin, MD, Division of Global Migration and Quarantine, National Center for Emerging and Zoonotic Infectious Diseases, CDC, Matthew Biggerstaff, MPH, Influenza Division, National Center for Immunization and Respiratory Diseases, CDC, Daniel Jernigan, MD, Influenza Division, National Center for Immunization and Respiratory Diseases, CDC, Carrie Reed, DSc, Influenza Division, National Center for Immunization and Respiratory Diseases, CDC. CDC Community Mitigation Guidelines Teams Coordination Team Alexandra Levitt, PhD, Office of Infectious Diseases; Narue Wright-Jegede, MPH, Neha Kanade, MPH, and Noreen Qualls, DrPH, Division of Global Migration and Quarantine, National Center for Emerging and Zoonotic Infectious Diseases, CDC. Abstraction Team Yao-Hsuan Chen, PhD, Charissa Dowdye, MPH, Hongjiang Gao, PhD, Narue Wright-Jegede, MPH, Neha Kanade, MPH, Jasmine Kenney, MPH, Erin Keyes, MPH, Tiffani Phelps, MPH, Noreen Qualls, DrPH, Jeanette Rainey, PhD, Jianrong Shi, MD, Karen Wong, MD, and Yenlik Zheteyeva, MD, Community Interventions for Infection Control Unit, Division of Global Migration and Quarantine, National Center for Emerging and Zoonotic Infectious Diseases, CDC. Consultation Team Maleeka Glover, ScD, Influenza Coordination Unit, Office of Infectious Diseases; Rita Helfand, MD, Office of the Director, National Center for Emerging and Zoonotic Infectious Diseases; Clive Brown, FRSPH, Martin Cetron, MD, Pamela Diaz, MD, Katrin Kohl, MD, PhD, David McAdam, MPA, and Jessica Reichard, Division of Global Migration and Quarantine, National Center for Emerging and Zoonotic Infectious Diseases; Bryan Christensen, PhD, Carolyn Gould, MD, Jeff Hageman, MD, John Jernigan, MD, and David Kuhar, MD, Division of Healthcare Quality Promotion, National Center for Emerging and Zoonotic Infectious Diseases; William Potts-Datema, MS, and Mary Vernon-Smiley, MD, Division of Adolescent and School Health, National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention; Belinda Smith and Teresa Smith, RN, Health Communication Science Office, National Center for Immunization and Respiratory Diseases; Carolyn Bridges, MD, and Samuel Graitcer, MD, Immunization Services Division, National Center for Immunization and Respiratory Diseases; Joseph Bresee, MD, Influenza Division, National Center for Immunization and Respiratory Diseases; Lisa Delaney, MD, and Chad Dowell, MD, Office of the Director, National Institute for Occupational Safety and Health; Samuel Groseclose, DVM, Laura Leidel, MSN, and Carol Pertowski, MD, Office of the Director, Office of Public Health Preparedness and Response; Steven Boedigheimer, MBA, Christa Singleton, MD, Theresa Smith, MD, and Todd Talbert, MA, Division of State and Local Readiness, Office of Public Health Preparedness and Response, CDC. Conflict of Interest The CDC contributors wish to disclose that they have no financial or competing interests or other relationships that would unfairly influence these CDC guidelines and recommendations. US Department of Health and Human Services/Centers for Disease Control and Prevention MMWR / April 21, 2017 / Vol. 66 / No. 1 25

Recommendations and Reports TABLE 1. Nonpharmaceutical interventions for personal and community preparedness to prevent pandemic influenza NPI category* NPIs Timing Personal Personal protective measures for Voluntary home isolation of ill persons (staying home when ill) Recommended at all times everyday use Respiratory etiquette Hand hygiene † Personal protective measures Voluntary home quarantine of exposed household members (staying home for up to 3 days Reserved for pandemics reserved for pandemics when a household member is ill) Use of face masks in community settings when ill Community § School closures and dismissals Temporary, preemptive, coordinated dismissals of child care facilities and schools for Reserved for pandemics ¶ grades K–12 Social distancing measures Dividing classes into smaller groups and creating opportunities for distance learning Reserved for pandemics (examples) (e.g., via the internet or local television or radio stations) Telecommuting and remote-meeting options in workplaces Mass gathering modifications, postponements, or cancellations Environmental Environmental surface cleaning Routine cleaning of frequently touched surfaces and objects in homes, child care facilities, Recommended at all times measures schools, and workplaces Abbreviation: NPI = nonpharmaceutical intervention. * Personal, community, and environmental NPIs should be 1) initiated early in a pandemic before local epidemics begin to grow exponentially, 2) targeted toward the nexus of transmission (in affected areas where the novel virus circulates), and 3) layered together to reduce community transmission to the greatest extent possible. † If the incubation period for the next pandemic influenza virus is longer or shorter than 3 days, CDC will amend the recommendation. § A school closure involves closing a school and sending all the students and staff members home. A school dismissal could involve a school staying open for staff members while the students stay home. ¶ Preemptive, coordinated dismissals might be implemented early during a pandemic to decrease the spread of influenza before many students and staff members become ill. Selective dismissals might be implemented by schools that serve students at high risk for complications from infection with influenza. Reactive dismissals might be implemented when many students and staff members are ill and not attending school or when many students and staff members are arriving at school ill and being sent home. Selective and reactive dismissals do not help slow disease transmission in the community. 26 MMWR / April 21, 2017 / Vol. 66 / No. 1 US Department of Health and Human Services/Centers for Disease Control and Prevention

Recommendations and Reports TABLE 2. Factors to consider before implementing nonpharmaceutical interventions during an influenza pandemic Planning factors Planning goals Activities Ethical considerations • Community engagement • Promoting public input into NPI planning in prepandemic planning • Ensuring that NPIs benefit all groups within a community • Equitable distribution of • Carefully considering and justifying any restrictions on individual freedom needed to implement public health resources NPIs (e.g., voluntary home quarantine of exposed household members) during a pandemic Feasibility of NPI • Minimal interruption of • Identifying practical obstacles to NPI implementation and considering ways to overcome them. implementation regular programs and Examples include the following: activities – Educational issues (e.g., missed educational opportunities or loss of free or subsidized school • Selection of NPIs that are meals because of school dismissals) practical to implement – Financial issues (e.g., workers who cannot afford to stay home when they are ill or to care for an within each community ill family member because they do not have paid sick leave) – Legal issues (e.g., local jurisdictions that do not have the legal authority to close schools or cancel mass gatherings for public health reasons) – Workplace issues (e.g., access to clean water, soap, or hand sanitizer and flexible workplace policies or arrangements) Activation triggers, • Optimal implementation • Maximizing the effectiveness of NPIs by taking the following actions: layering, and duration of NPIs during a pandemic – Identifying activation triggers to ensure early implementation of NPIs before explosive growth of NPIs of the pandemic – Planning for simultaneous use of multiple NPIs because each NPI is only partially effective – Planning for long-term duration of school dismissals and social distancing measures Selecting NPIs for groups • Protection of persons most • Identifying strategies for implementing NPIs among groups at high risk for severe influenza-related at risk for severe influenza at risk for severe illness or complications, including the following: complications and for death during a pandemic – Pregnant women those with limited access • Protection of persons who – Persons aged <5 yrs and ≥65 yrs to care and services might need additional – Persons with underlying chronic diseases assistance during a – Persons in institutions pandemic response, • Identifying strategies for implementing NPIs among groups who might experience barriers to or including persons with difficulties with accessing or receiving medical care and services, including the following: disabilities and other – Persons who are culturally, geographically, or socially isolated or economically disadvantaged access and functional – Persons with physical disabilities, limitations, or impairments needs – Persons with low incomes, single-parent families, and residents of public housing – Persons who live in medically underserved communities Public acceptance of NPIs • Active participation in NPI • Promoting public understanding that individual action is essential for effective implementation of implementation during a NPIs in every pandemic scenario. In many scenarios, both personal and community NPIs might be pandemic recommended. NPI recommendations might change as new knowledge is gained. • Identifying key personnel to disseminate emergency information (e.g., alerts, warnings, and notifications) and establishing communication channels that enable members of the public to ask questions and express concerns (e.g., call centers or social media sites) • Ensuring that school dismissals and other NPIs are acceptable to the community during a pandemic • Coordinating with local partners to support households complying with voluntary home quarantine (e.g., providing necessary food and supplies) • Identifying strategies for mitigating the secondary consequences of school dismissals and other social distancing measures (e.g., modifications or cancellations of mass gatherings) • Minimizing intervention fatigue* during a pandemic Balancing public health • Maximization of NPI public • Estimating economic and social costs of NPIs and their secondary (unintended or unwanted) benefits and social costs health benefits and consequences minimization of social and • Balancing those costs against public health benefits, with reference to different prepandemic economic costs during a planning scenarios pandemic • Identifying strategies for reducing the cost of NPI implementation Monitoring and evaluation • Ongoing guidance during • Identifying ways to monitor and evaluate the following: of NPIs a pandemic on optimal – Degree of transmission and severity of the evolving pandemic NPI implementation, – Type and degree of NPI implementation maintenance, and – Level of compliance with NPI measures and the emergence of intervention fatigue discontinuation – Effectiveness of NPIs in mitigating pandemic impact – Secondary consequences of NPIs and the effectiveness of strategies to mitigate them Abbreviation: NPI = nonpharmaceutical intervention. Source: Adapted from: Barrios LC, Koonin LM, Kohl KS, Cetron M. Selecting nonpharmaceutical strategies to minimize influenza spread: the 2009 influenza A (H1N1) pandemic and beyond. Public Health Rep 2012;127:565–71. * Fatigue that results from being requested, often repeatedly, to change daily behaviors for the good of the community, especially when those changes disrupt daily life (e.g., caring for children when schools are dismissed for several weeks or avoiding crowded settings) (Source: Ryan JR, ed. Pandemic influenza: emergency planning and community preparedness. 2008. Boca Raton, FL: CRC Press; 2008:158). US Department of Health and Human Services/Centers for Disease Control and Prevention MMWR / April 21, 2017 / Vol. 66 / No. 1 27

Recommendations and Reports TABLE 3. Examples of possible nonpharmaceutical intervention surveillance indicators for an influenza pandemic Key influenza indicator U.S. data source Measure of influenza activity Indicators of spread or level of influenza activity Percentage of patient visits to Outpatient ILI Surveillance Network Current ILI level in relation to most recent national and region-specific health care providers for ILI in the (ILINet), which includes approximately baseline levels, with CDC providing baseline values for the 10 HHS United States 2,900 enrolled outpatient health care surveillance regions and for the United States as a whole providers in 50 states https://www.cdc.gov/flu/weekly/overview.htm ILI activity by state: percentage of Outpatient ILI Surveillance Network Ten activity levels that compare the mean reported percent of visits due to ILI outpatient visits for ILI in a state (ILINet) for the current week to noninfluenza weeks, specifying the number of (ranges from minimal to high) Additional: Flu Near You https:// standard deviations at or above the mean for the current week flunearyou.org/ https://www.cdc.gov/flu/weekly/FluViewInteractive.htm Geographic spread of influenza in a State and Territorial Epidemiologists Estimated weekly levels of geographic spread (local, regional, or widespread) state (ranges from none to reports of influenza activity reported by state health departments widespread) https://www.cdc.gov/flu/weekly/overview.htm Percentage of respiratory specimens Approximately 110 U.S. WHO collaborating National and regional percentage of respiratory specimens testing positive that test positive for influenza laboratories and 240 National Respiratory for influenza viruses viruses in the United States and Enteric Virus Surveillance System https://www.cdc.gov/flu/weekly/FluViewInteractive.htm laboratories Absenteeism rates due to ILI in child ILI monitoring/surveillance systems in Increased absenteeism rates due to ILI in child care facilities, K-12 schools, or care facilities, K–12 schools, or child care facilities, K–12 schools, or colleges and universities (reflects increased number of ILI cases) colleges and universities (reflects colleges and universities number of ILI cases) Laboratory-confirmed influenza Increases in laboratory-confirmed influenza cases among students, teachers, cases among students, teachers, and staff members and staff members Laboratory-confirmed outbreaks of influenza in child care facilities, K–12 schools, or colleges and universities Indicators of clinical severity of influenza Influenza-associated Influenza Hospitalization Surveillance Population-based rate of influenza-associated hospitalizations in multiple hospitalizations Network (FluSurv-NET), which collects geographic areas data from the 10 Emerging Infections https://www.cdc.gov/flu/weekly/FluViewInteractive.htm Program sites, as well as Michigan, Ohio, and Utah (https://wwwnc.cdc.gov/eid/ article/21/9/14-1912_ article#keycomponentsofflusurv-net) Percentage of deaths attributed to National Center for Health Statistics The percentage of death certificates indicating pneumonia and influenza pneumonia and influenza mortality surveillance system compared with a seasonal baseline and epidemic threshold value calculated for each week (using a periodic regression model) https://www.cdc.gov/flu/weekly Influenza-associated deaths among Influenza-Associated Pediatric Mortality Any laboratory-confirmed influenza-associated deaths in children, all of persons aged <18 yrs Surveillance System which are reported through this system https://www.cdc.gov/flu/weekly/FluViewInteractive.htm Abbreviations: HHS = U.S. Department of Health and Human Services; ILI = influenza-like illness; WHO = World Health Organization. 28 MMWR / April 21, 2017 / Vol. 66 / No. 1 US Department of Health and Human Services/Centers for Disease Control and Prevention

Recommendations and Reports TABLE 4. CDC novel influenza virus pandemic intervals TABLE 5. Initial assessment: scaled measures of influenza virus Intervals Indicators transmissibility and clinical severity Investigation: This interval is indicated by the identification of an Scale Investigation of novel animal case of influenza A subtype with potential Measures of transmissibility Low to Moderate to influenza cases implications for human health or identification of and clinical severity moderate high a human case of novel influenza A anywhere in Transmissibility the world. Secondary attack rate, household ≤20% >20% Recognition: This interval is indicated by an increasing number Attack rate, school or university ≤30% >30% Recognition of of cases or clusters of novel influenza A in humans Attack rate, workplace or community ≤20% >20% potential for ongoing and by virus characteristics indicating potential for R : basic reproductive number 1–1.7 ≥1.8 0 transmission ongoing human-to-human transmission Underlying population immunity Some underlying Little to no anywhere in the world. population underlying Initiation: Initiation of This interval is indicated by confirmation of cases of immunity population the pandemic wave novel influenza A in humans and demonstration immunity of efficient and sustained human-to-human Emergency department or other <10% ≥10% transmission anywhere in the world. outpatient visits for influenza-like illness Acceleration: This interval is indicated by an increasing rate of Virologic characterization Genetic markers Genetic Acceleration of the novel influenza A cases identified nationally, for markers for pandemic wave indicating establishment in the country. transmissibility transmissibility absent present Deceleration: This interval is indicated by decreasing rates of Deceleration of the novel influenza A infection. Animal models, transmission studies Less efficient or More efficient pandemic wave similar to than seasonal seasonal influenza Preparation: This interval is indicated by sporadic cases of novel influenza Preparation for a influenza A infection and surveillance rates Clinical severity future pandemic wave returning to baseline. Upper bound of case-fatality ratio <1% ≥1% Source: Holloway R, Rasmussen SA, Zaza S, Cox NJ, Jernigan DB; Influenza Upper bound of case-hospitalization ratio <10% ≥10% Pandemic Framework Workgroup. Updated preparedness and response Deaths-hospitalizations ratio <10% ≥10% framework for influenza pandemics. MMWR Recomm Rep 2014;63(No. RR-6). Virologic characterization Genetic markers Genetic for virulence markers for absent virulence present Animal models, evaluation of morbidity Less virulent or More virulent and mortality similar to than seasonal seasonal influenza influenza Source: Reed C, Biggerstaff M, Finelli L, et al. Novel framework for assessing epidemiologic effects of influenza epidemics and pandemics. Emerg Infect Dis 2013;19:85–91. TABLE 6. Refined assessment: scaled measures of influenza virus transmissibility and clinical severity Scale Measures of transmissibility and clinical severity 1 2 3 4 5 6 7 Transmissibility (scale of 1–5) Symptomatic attack rate, community ≤10% 11%–15% 16%–20% 21%–24% ≥25% — — Symptomatic attack rate, school ≤20% 21%–25% 26%–30% 31%–35% ≥36% — — Symptomatic attack rate, workplace ≤10% 11%–15% 16%–20% 21%–24% ≥25% — — Household secondary attack rate, symptomatic ≤5% 6%–10% 11%–15% 16%–20% ≥21% — — R : basic reproductive number ≤1.1 1.2–1.3 1.4–1.5 1.6–1.7 ≥1.8 — — 0 Peak percentage of outpatient visits for influenza-like illnes 1%–3% 4%–6% 7%–9% 10%–12% ≥13% — — Clinical severity (scale of 1–7) Case-fatality ratio <0.02% 0.02%–0.05% 0.05%–0.1% 0.1%–0.25% 0.25%–0.5% 0.5%–1% >1% Case-hospitalization ratio <0.5% 0.5%–0.8% 0.8%–1.5% 1.5%–3% 3%–5% 5%–7% >7% Deaths-hospitalizations ratio ≤3% 4%–6% 7%–9% 10%–12% 13%–15% 16%–18% >18% Source: Reed C, Biggerstaff M, Finelli L, et al. Novel framework for assessing epidemiologic effects of influenza epidemics and pandemics. Emerg Infect Dis 2013;19:85–91. US Department of Health and Human Services/Centers for Disease Control and Prevention MMWR / April 21, 2017 / Vol. 66 / No. 1 29

Recommendations and Reports TABLE 7. Process for developing the community mitigation guidelines for pandemic influenza, October 2011–October 2016 Topic Comment Goal of the guidelines The goal of the 2017 guidelines is to update the 2007 guidance and provide updated recommendations on the use of NPIs during an influenza pandemic in the United States, based on lessons learned from the 2009 H1N1 pandemic and on an expanded evidence base for NPIs that includes studies conducted since 2007. Users of the guidelines State, tribal, local, and territorial public health authorities Population and settings The updated 2017 planning guidelines apply but are not limited to activities conducted by public health authorities who are responsible for facilitating and implementing emergency preparedness, planning, and response efforts in community settings (e.g., schools, workplaces, and mass gatherings). Developer of the guidelines The CDC Community Mitigation Guidelines Work Group convened in October 2012. The group is composed of staff from CDC’s Office of Infectious Diseases, Influenza Coordination Unit, National Center for Emerging and Zoonotic Infectious Diseases, and National Center for Immunization and Respiratory Diseases. The work group members are subject-matter experts in seasonal and pandemic influenza, community mitigation measures, NPIs, epidemiology, health policy, and technical guidelines development. The work group provided technical oversight, coordinated the guidelines development process, and contributed to the writing of the updated guidelines. Development of the guidelines The updated planning guidelines are based on a NPI report developed beginning in October 2011 and finalized in August 2013. The NPI report was developed for internal CDC discussions and served as the foundation for updating the NPI recommendations from the 2007 guidance. Evidence collection The NPI recommendations in the 2017 guidelines are based on studies published in English-language, peer-reviewed journals through September 2016. The evidence base for NPIs includes systematic literature reviews, metaanalyses, and evidence from epidemiologic studies, laboratory experiments, and modeling simulations. Method for data synthesis Staff members from CDC’s Community Interventions for Infection Control Unit worked in pairs to ensure quality control. They reviewed, abstracted, synthesized, and entered approximately 191 articles into spreadsheets to help establish the overall NPI body of literature, including the evidence base for NPIs. Development of the recommendations The approach used by the Guide to Community Preventive Services (The Community Guide) was adapted and applied to develop the NPI recommendations in the updated planning guidelines. Planning guides To help operationalize the updated guidelines, six community mitigation prepandemic planning guides have been developed for key populations and decision-makers in community settings. During September–October 2015, before submission for CDC clearance, the National Public Health Information Coalition facilitated discussion of the planning guides by representatives of the public health, education, and business communities. The guides are part of a set of practical, user-friendly, and plain-language companion implementation materials. Updating the guidelines The 2017 guidelines will be updated when new information warrants their modification. Abbreviation: NPI = nonpharmaceutical intervention. TABLE 8. Number of selected peer-reviewed articles on nonpharmaceutical interventions used to develop community mitigation guidelines for pandemic influenza, by NPI type and measure and by article topic Number and type of articles reviewed* NPI type and measure Background Evidence based† Implementation issues Personal NPIs Personal protective measures for everyday use § Voluntary home isolation 2 7 1 Respiratory etiquette 2 0 3 Hand hygiene 3 15 11 Personal protective measures reserved for pandemics § Voluntary home quarantine 1 0 3 Use of face masks in community settings 0 18 4 Community NPIs School closures and dismissals 24 25 26 Social distancing measures for schools, workplaces, and mass 10 12 11 gatherings Environmental NPIs Environmental surface cleaning measures 1 12 0 Abbreviation: NPI = nonpharmaceutical intervention. * Articles that are cited in more than one section in the supplementary document (supplementary Chapter 3 https://stacks.cdc.gov/view/cdc/44313) are not counted twice in this table. † Of the 89 evidence-based articles, 27 articles assessed the effectiveness of NPIs when used in combination with one another. The evidence-based articles include 14 systematic literature reviews and metaanalyses composed of approximately 475 individual studies that were reviewed and analyzed by their respective authors. These studies contribute to the overall body of literature on NPIs and help support the evidence base on the effectiveness of NPIs. They are provided (supplementary Appendix 6 https://stacks.cdc.gov/view/cdc/44314) but are not accounted for in this table because CDC staff members did not re-review them. § Voluntary home isolation and voluntary home quarantine share the same set of evidence-based articles. 30 MMWR / April 21, 2017 / Vol. 66 / No. 1 US Department of Health and Human Services/Centers for Disease Control and Prevention

Recommendations and Reports TABLE 9. Prepandemic influenza planning scenarios to guide implementation of nonpharmaceutical interventions, by severity of pandemic and the Pandemic Severity Assessment Framework quadrant Possible no. of hospitalizations and † Implications of clinical deaths if unmitigated, by age group Severity of pandemic severity and transmissibility Age groups No. of No. of and PSAF quadrant in this scenario* (yrs) hospitalizations deaths Historical experience Low to moderate • Clinical severity and All ages 340,000 17,000 2009 pandemic severity (mild to transmissibility similar to the 0–18 50,000 1,000 • First detected in North America, the 2009 H1N1 moderate pandemic) range seen during annual 18–64 135,000 6,000 pandemic quickly spread to all continents. In the PSAF quadrant: A influenza seasons. ≥65 155,000 10,000 United States, persons at high risk for severe • Estimated overall attack and complications included pregnant women and those case-fatality rates: 18% and with neuromuscular disease, lung disease, morbid 0.03%, respectively. Rates of obesity, and other chronic conditions. severe outcomes are greater • An estimated 43–89 million people in the United among younger persons than States became ill with H1N1 from April 2009 through § during influenza seasons. April 2010, and approximately 12,000 people died. A total of 87% of deaths were among persons aged ≤65 yrs, with a mean age of 43 yrs.¶ During typical influenza seasons, 80%–90% of deaths are among persons aged ≥65 yrs, and the mean age of influenza- related deaths is approximately 76 yrs.** Moderate to high • Clinical severity similar to the range All ages 550,000 35,000 1968 pandemic severity (moderate to seen during annual influenza 0–18 80,000 2,500 • First detected in Hong Kong in July 1968, a new severe pandemic) seasons. Transmissibility greater 18–64 220,000 12,000 influenza virus (H3N2) spread worldwide. PSAF quadrant: B than during influenza seasons. ≥65 250,000 20,000 • The first cases in the United States were detected in • Estimated overall attack and September 1968. The 1968 influenza pandemic case–fatality rates: 22% and 0.05%, resulted in approximately 30,000 deaths in the respectively. Rates of severe United States, with approximately half among those outcomes are greater than during aged ≥65 yrs.††,§§ influenza seasons, especially among younger persons. High severity (severe • Clinical severity similar to the range All ages 1,100,000 86,000 1957 pandemic pandemic) seen during annual influenza 0–18 150,000 6,000 • A new influenza virus, H2N2 (the Asian strain), PSAF quadrant: B seasons. Transmissibility greater 18–64 450,000 30,000 emerged in China in February 1957 and spread to than during influenza seasons. ≥65 500,000 50,000 approximately 20 countries, including the United • Estimated overall attack and States, by June 1957. case-fatality rates: 28% and 0.1%, • An estimated 25% of the U.S. population became ill respectively. Rates of severe with the new pandemic virus strain. U.S. infection outcomes are greater than during rates were highest among school-aged children and influenza seasons. adults aged ≤40 yrs, with most (64%) of the approximately 70,000 deaths occurring among older adults.††,§§,¶¶ Very high severity • Both clinical severity and All ages 7,500,000 1,400,000 1918 pandemic (very severe to transmissibility are greater than 0–18 1,000,000 100,000 • The 1918 pandemic resulted in death for 2%–3% of extreme pandemic) during annual influenza seasons. 18–64 3,000,000 500,000 those infected, a case-fatality rate that was much PSAF quadrant: D • Estimated overall attack and ≥65 3,400,000 800,000 greater than the rate during an average influenza case-fatality rates: 30% and 1.5%, season. The pandemic virus was easily transmitted. respectively. Rates of severe • Approximately one fourth of the U.S. population outcomes are greater than during became ill, and approximately 500,000 died; 99% of influenza seasons, especially deaths occurred in persons aged ≤65 yrs.††,*** among young adults. Abbreviation: PSAF = Pandemic Severity Assessment Framework. * Based on PSAF (Source: Reed C, Biggerstaff M, Finelli L, et al. Novel framework for assessing epidemiologic effects of influenza epidemics and pandemics. Emerg Infect Dis 2013;19:85–91). † Point estimates for hospitalizations and deaths, by age group, are based on the estimated overall attack and case-fatality rates provided in the second column (clinical severity and transmissibility). Age-specific point estimates of hospitalizations and deaths are based on U.S. Census 2010 population data. § Source: Shrestha SS, Swerdlow DL, Borse RH, et al. Estimating the burden of 2009 pandemic influenza A (H1N1) in the United States (April 2009–April 2010). Clin Infect Dis 2011;52(Suppl 1):S75–S82. ¶ Source: Fowlkes AL, Arguin P, Biggerstaff MS, et al. Epidemiology of 2009 pandemic influenza A (H1N1) deaths in the United States, April–July 2009. Clin Infect Dis 2011;52(Suppl 1):S60–S68. ** Source: Viboud C, Miller M, Olson DR, Osterholm M, Simonsen L. Preliminary estimates of mortality and years of life lost associated with the 2009 A/H1N1 pandemic in the U.S. and comparison with past influenza seasons. PLoS Currents 2010;2:RRN1153. †† Source: Simonsen L, Clarke MJ, Schonberger LB, Arden NH, Cox NJ, Fukuda K. Pandemic versus epidemic influenza mortality: a pattern of changing age distribution. J Infect Dis 1998;178:53–60. §§ Source: Cox NJ, Subbarao K. Global epidemiology of influenza: past and present. Annu Rev Med 2000;51:407–21. ¶¶ Source: Henderson DA, Courtney B, Inglesby TV, Toner E, Nuzzo JB. Public health and medical responses to the 1957–58 influenza pandemic. Biosecur Bioterror 2009;7:265–73. *** Source: Collins SD. Age and sex incidence of influenza and pneumonia morbidity and mortality in the epidemic of 1928–29 with comparative data for the epidemic of 1918–19. Public Health Rep 1931;46:1909–37. US Department of Health and Human Services/Centers for Disease Control and Prevention MMWR / April 21, 2017 / Vol. 66 / No. 1 31

Recommendations and Reports TABLE 10. Recommended nonpharmaceutical interventions for influenza pandemics, by setting and pandemic severity* Pandemic severity Low to moderate severity High severity Very high severity † Setting (mild to moderate pandemic) (severe pandemic) (very severe to extreme pandemic ) All CDC recommends voluntary home CDC recommends voluntary home CDC recommends voluntary home isolation of ill isolation of ill persons, respiratory isolation of ill persons, respiratory persons, respiratory etiquette, hand hygiene, and etiquette, hand hygiene, and etiquette hand hygiene, and routine routine cleaning of frequently touched surfaces routine cleaning of frequently cleaning of frequently touched and objects. § touched surfaces and objects. surfaces and objects. Residences CDC generally does not recommend CDC might recommend voluntary CDC might recommend voluntary home voluntary home quarantine of home quarantine of exposed quarantine of exposed household members in exposed household members. household members in areas where areas where novel influenza virus circulates. novel influenza virus circulates. CDC generally does not recommend CDC might recommend use of face CDC might recommend use of face masks by ill use of face masks by ill persons. masks by ill persons when crowded persons when crowded community settings community settings cannot be avoided. cannot be avoided. Child care facilities, schools for CDC might recommend selective CDC might recommend temporary CDC might recommend temporary preemptive, grades K–12, and colleges school dismissals in facilities serving preemptive, coordinated dismissals coordinated dismissals of child care facilities and universities children at high risk for severe of child care facilities and schools.¶ and schools. influenza complications. If schools remain open, CDC might If schools remain open, CDC might recommend recommend social distancing social distancing measures. measures.** Workplaces CDC generally does not recommend CDC might recommend social CDC might recommend social distancing measures. social distancing measures. distancing measures.†† Mass gatherings§§ CDC generally does not recommend CDC might recommend modifications, CDC might recommend modifications, modifications, postponements, or postponements, or cancellations. postponements, or cancellations. cancellations. Abbreviation: NPI = nonpharmaceutical intervention. * Personal, community, and environmental NPIs should be 1) initiated early in a pandemic before local epidemics begin to grow exponentially, 2) targeted toward the nexus of transmission (in affected areas where the novel virus circulates), and 3) layered together to reduce community transmission to the greatest extent possible. † During a very severe or extreme pandemic (similar to the 1918 pandemic), CDC is likely to take an aggressive stance and recommend certain additional NPIs. § Recommended NPIs are the same for seasonal influenza. ¶ Preemptive, coordinated dismissals might be implemented early during a pandemic to decrease the spread of influenza before many students and staff members become ill. Selective dismissals might be implemented by schools that serve students at high risk for complications from infection with influenza. Reactive dismissals might be implemented when many students and staff members are ill and not attending school or when many students and staff members are arriving at school ill and being sent home. Selective and reactive dismissals do not help slow disease transmission in the community. ** Social distancing measures that reduce face-to-face contact in schools might include dividing classes into smaller groups of students who are spaced further apart from each other within the classroom. †† Social distancing measures that reduce face-to-face contact in workplaces might include offering telework and remote meeting options. Flexible sick leave policies should be implemented to encourage workers to stay home if needed. §§ In all scenarios, mass gathering attendance during local outbreaks should be discouraged for persons at high risk for severe influenza-related complications. 32 MMWR / April 21, 2017 / Vol. 66 / No. 1 US Department of Health and Human Services/Centers for Disease Control and Prevention

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