WHO surveillance case definitions for ILI and SARI
Case definitions for influenza surveillance
As of January 2014
The WHO global influenza surveillance standards define the surveillance case definitions for influenza-like illness (ILI) and severe acute respiratory infections (SARI).
Key messages when using the case definitions:
- Influenza infection causes a clinical syndrome not easily distinguished from other respiratory infections.
- The case definitions for ILI and SARI are not necessarily intended to capture all cases but to describe trends over time.
- Using one common case definition globally will allow national health authorities to interpret their data in an international context.
ILI case definition
An acute respiratory infection with:
- measured fever of ≥ 38 C°
- and cough;
- with onset within the last 10 days.
SARI case definition
An acute respiratory infection with:
- history of fever or measured fever of ≥ 38 C°;
- and cough;
- with onset within the last 10 days;
- and requires hospitalization.
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WHO Global Epidemiological Surveillance Standards for Influenza
pdf, 1.58Mb
Guideline describing standards for influenza surveillance including case definitions for ILI and SARI
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Revision of clinical case definitions: influenza-like illness and severe acute respiratory infection
From the Bulletin of the World Health Organization, Volume 06, February 2018