Pandemic influenza severity assessment (PISA): a WHO guide to assess the severity of influenza in seasonal epidemics and pandemics
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World Health Organization
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x, 32 p.
This second edition of the WHO pandemic influenza severity assessment (PISA) guide provides an updated framework for assessing the severity of influenza epidemics and pandemics using routine surveillance data. The guidance outlines a systematic approach for interpreting influenza and syndromic respiratory illness activity in relation to historical trends, with the aim of supporting risk communication, public health decision-making, preparedness and response activities. Building on the original 2017 framework and lessons learned from the COVID-19 pandemic, the document expands the assessment model to include four indicators: transmissibility, seriousness of disease, morbidity and mortality, and impact on health care capacity. The guide describes methods for selecting surveillance parameters, establishing thresholds using historical data, interpreting severity findings and communicating results nationally and globally. It also introduces updated approaches for syndromic surveillance, threshold setting and the use of modelling metrics, while emphasizing flexibility according to national surveillance capacities and contexts. The document is intended primarily for public health professionals responsible for influenza surveillance and severity assessment at the national level and contributes to strengthening pandemic preparedness and collaborative respiratory disease surveillance.
This second edition of the WHO pandemic influenza severity assessment (PISA) guide provides an updated framework for assessing the severity of influenza epidemics and pandemics using routine surveillance data. The guidance outlines a systematic approach for interpreting influenza and syndromic respiratory illness activity in relation to historical trends, with the aim of supporting risk communication, public health decision-making, preparedness and response activities. Building on the original 2017 framework and lessons learned from the COVID-19 pandemic, the document expands the assessment model to include four indicators: transmissibility, seriousness of disease, morbidity and mortality, and impact on health care capacity. The guide describes methods for selecting surveillance parameters, establishing thresholds using historical data, interpreting severity findings and communicating results nationally and globally. It also introduces updated approaches for syndromic surveillance, threshold setting and the use of modelling metrics, while emphasizing flexibility according to national surveillance capacities and contexts. The document is intended primarily for public health professionals responsible for influenza surveillance and severity assessment at the national level and contributes to strengthening pandemic preparedness and collaborative respiratory disease surveillance.