1. What is PISA?

The pandemic influenza severity assessment tool (hereby referred to as ‘PISA’), is used to describe the severity of influenza in seasonal epidemics and pandemics, when influenza viruses are spreading from one person to another. It compares current influenza activity to that of the past in order to judge the severity of the current influenza season or pandemic. This assessment could help countries decide on what measures to put in place to control an influenza epidemic or pandemic. A more severe influenza pandemic may require more urgent and intense response measures compared to a less severe influenza pandemic.

2. Why was PISA established?

WHO is concerned about all flu pandemics, but is uncertain as to when, from where, by which strain the next pandemic will emerge, and how severe the next pandemic may be.

The devastating pandemic of 1918 which caused an estimated 50 million to 100 million deaths worldwide, three influenza pandemics have occurred - in 1957, 1968 and 2009 - but of significantly less severity. Following the events of the most recent 2009 influenza pandemic (H1N1), in 2011, the World Health Assembly recommended that WHO should develop and apply measures that can be used to assess the severity of every influenza epidemic, whether seasonal or pandemic. As a result, PISA was launched in March 2017 as a more systematic approach to assess influenza severity.

3. Who should implement PISA?

PISA is intended for use by Member States and WHO as part of their overall influenza epidemic and pandemic risk assessments.

4. Why is assessing influenza severity important?

An influenza severity assessment is important since it provides the information needed to determine the timing, scale, emphasis, intensity and urgency of pandemic response actions.

5. Why is it important to assess influenza severity both during seasonal epidemics as well as pandemics?

By applying, evaluating and refining tools to assess seasonal influenza activity, WHO and countries can be better prepared to assess severity in a timely manner in the next pandemic. During a pandemic, resources and time are limited. Becoming familiar with PISA during seasonal influenza epidemics is key to enhancing its utility and reliability during the pandemic period.

6.How does PISA work?

PISA is an important use of routine surveillance data and relies on the qualitative assessments of four indicators to assess the severity of influenza epidemics. These indicators are: transmissibility, seriousness of influenza disease, morbidity and mortality, and the impact on healthcare capacity.

7. How does PISA benefit countries?

PISA helps countries to describe their current epidemiological situation, to assess the severity of an influenza epidemic or pandemic based on all available information, to inform national and global risk assessments, and to inform public health preparedness, response and recovery measures, as well as resource allocation.

8. Does PISA require its own unique surveillance system?

The PISA methodology has been developed to be flexible, timely and based on existing country surveillance systems. It does not require the development of new systems.

9. How is WHO supporting Member States to implement PISA?

WHO continues to encourage all countries to become familiar with PISA and provides support to Member States to implement PISA.

 

Contact influenza@who.int with any further questions or comments.