# Establishing Pandemic Influenza Severity Assessment (PISA) parameters and thresholds for Canada’s FluWatch program

## TL;DR

This paper describes how Canada developed and validated thresholds to assess influenza pandemic severity using data from 2014–2019, aiming to improve pandemic response.

## Contribution

The study establishes and validates national PISA thresholds for influenza severity assessment within Canada’s FluWatch program.

## Key findings

- PISA thresholds showed good agreement with FluWatch epidemiologists' seasonal assessments.
- Thresholds were developed for transmissibility, disease seriousness, and impact indicators.
- Canada will implement weekly PISA assessments in the 2023–2024 season to monitor influenza activity.

## Abstract

The World Health Organization (WHO) developed a structured framework to enable countries to rapidly assess the severity of an influenza pandemic. This framework, the Pandemic Influenza Severity Assessment (PISA), is intended to be performed weekly during seasonal epidemics so that assessing influenza severity during a pandemic can be done with greater ease and efficiency.

Using influenza surveillance indicators within Canada’s FluWatch program from seasons 2014–2015 to 2018–2019, national PISA thresholds were developed and assessed against seasonal data for seasons 2019–2020 to June of 2022–2023.

Canada developed thresholds for each required indicator (transmissibility, seriousness of disease and impact) for multiple WHO-recommended parameters. The thresholds were assessed against four seasons, and it was determined that there was a good agreement between the PISA assessments and the characterization of the season by FluWatch epidemiologists.

With confidence in the validity of the PISA thresholds, the FluWatch program will begin to share PISA assessments weekly through the FluWatch report in the 2023–2024 seasons to help characterize influenza activity in Canada and inform responses to the seasonal influenza epidemic.