Effect of screening case definitions on estimates of influenza-associated hospitalization annual incidence, Vadu, District Pune, India, May 2009–April 2011.

*% underestimate defined as ((1-estimated hospitalization incidence based on use of the given screening definition)/estimated hospitalization incidence based on use of all acute medical hospitalizations as a screening definition) expressed as a percentage). **Influenza-like illness (ILI) was defined as fever and either cough or sore throat. ***Acute respiratory illness (ARI) was defined as >1 of the following: cough, nasal discharge, sore throat, or shortness of breath (based on history). †Febrile acute respiratory illness (FARI) was defined as the presence of ARI plus fever. ‡For persons >5 years, severe acute respiratory illness (SARI) was defined as the presence of ILI and either shortness of breath or difficulty breathing. For children <5 years, SARI was defined as pneumonia or severe pneumonia as defined by the Integrated Management of Childhood Illness guidelines as any of the following: any general danger sign (i.e. unable to drink or breastfeed, vomiting, convulsions, lethargic, or unconscious), chest indrawing, stridor, or fast breathing on examination.