The potential of pre-diagnostic data sources for influenza surveillance

Traditionally, influenza is monitored via passive surveillance, which is often neither timely nor likely to identify an outbreak early in its course. Early detection of influenza epidemics could prevent significant morbidity and mortality and as a result the emphasis of research has changed to investigate early indicators for detection. This review identifies the strengths and weaknesses of data sources available for influenza surveillance and their potential impact on infection control resources.