Pandemic Severity Assessment Framework (PSAF) When a novel influenza virus has emerged and circulates in human populations with efficient and sustained transmission, the public health impact posed by the pandemic can begin to be assessed. The PSAF uses information available from surveillance, investigations, initial case series, and other sources to help predict how severe the impact of the pandemic will be compared with past seasonal and pandemic experiences. Although the IRAT focuses on the risk of emergence and potential for impact before a pandemic begins, the PSAF focuses instead on epidemiologic parameters of transmissibility and severity after the virus emerges with efficient and sustained transmission in humans. The PSAF can be used early in a pandemic, with assessments repeated as information evolves, but determination of an initial assessment requires a sufficient number of human cases and clusters of illness to be identified and characterized. Depending on the number of cases, size of clusters, and the geographic locations of outbreaks, the trigger for using PSAF is likely to occur during the early initiation interval when a pandemic is beginning. The PSAF can be updated regularly as the pandemic progresses. The PSAF is based on transmissibility and clinical severity parameters and uses different scales for 1) initial assessments and 2) more refined assessments when more data become available. The initial assessment, performed early in the outbreak when there might be uncertainty about viral characteristics resulting from limited epidemiologic data, uses a dichotomous scale of low-to-moderate versus moderate-to- high transmissibility and severity. The refined assessment, performed when more reliable data are available, uses a 5-point scale for transmissibility and a 7-point scale y. After available data a for clinical severit re assessed on these scales, the overall results are plotted as a two-dimensional chart, with the measures of transmissibility along the y-axis and the measures of severity along the x-axis. The PSAF results can be compared with referent points, such as previous pandemics or particularly severe influenza seasons.13 13 Reed C, Biggerstaff M, Finelli L, Koonin LM, Beauvais D, Uzicanin A, et al. Novel framework for assessing epidemiologic effect of influenza epidemics and pandemics. Emerg Infect Dis 2013 Jan;19(1):85-91. 51