Central Data Catalog

Case definitions for influenza surveillance need to be simple, easily understood and easily implemented. The international standardization of such case definitions is difficult, partly because the optimal choice of case definition depends on the population involved and the objectives of the surveillance. The World Health Organization (WHO) arranged a consultation on this topic in 2011 and is currently developing a document to describe minimum global standards for influenza surveillance case definitions. In the surveillance of severe influenza requiring hospitalization, the WHO currently recommends a particular case definition for severe acute respiratory illness: “cough or sore throat, plus measured fever, shortness of breath and need for hospitalization”(Table 1). In the surveillance of outpatient influenza, however, WHO recommends using the case definition for influenza-like illness (measured fever plus cough or sore throat). Despite this recommendation, in some countries, a case definition for acute respiratory illness is used to evaluate outpatient influenza.