Bulletin of the World Health Organization

Performance of case definitions used for influenza surveillance among hospitalized patients in a rural area of India

Siddhivinayak Hirve, Mandeep Chadha, Pallavi Lele, Kathryn E Lafond, Avinash Deoshatwar, Somnath Sambhudas, Sanjay Juvekar, Anthony Mounts, Fatimah Dawood, Renu Lal & Akhilesh Mishra

Volume 90, Number 11, November 2012, 804-812

Table 1. Commonly used World Health Organization (WHO) case definitions for influenza surveillance

Illness Case definition
Influenza-like illness Sudden-onset fever (> 38 °C) with cough or sore throat, in the absence of other diagnosesa
Severe acute respiratory illness Cases aged ≥ 5 years should meet the case definition for ILI, require hospital admission and have shortness of breath and/or difficulty breathing.
Younger cases should meet the IMCI programme case definition for either pneumonia or severe pneumonia. The definitions are as follows:
– Pneumonia: cough or difficulty breathing plus a respiratory rate above 40 breaths per minute (if child aged 1–5 years) or 50 breaths per minute (if child aged 2–12 months).
– Severe pneumonia (in children aged 2 months–5 years): requires hospital admission and has cough or difficulty breathing plus any of six general danger signs: inability to drink or breastfeed, vomiting of everything, convulsions, lethargy or unconsciousness, chest in-drawing and/or stridor in a calm child.
Acute respiratory illnessb Sudden onset, clinician’s judgment that the illness is the result of infection, and at least one of four respiratory symptoms (cough, sore throat, shortness of breath and/or nasal discharge)
Febrile acute respiratory illness Meets ARI definition and has fever

ARI, acute respiratory illness; IMCI, Integrated Management of Childhood Illness; ILI, influenza-like illness.

a Fever to be measured and not just based on history of fever or feverishness.

b The definition shown is that commonly used in the WHO European Region. WHO’s global ARI definition is identical to the case definition for ILI.