A comparison of data sources for the surveillance of seasonal and pandemic influenza in Victoria.

Understanding the characteristics of available influenza or influenza-like illness (ILI) surveillance systems is important for seasonal influenza surveillance and pandemic preparedness. We compared five influenza or ILI data sources in Victoria: notifications of laboratory-confirmed influenza to the Victorian Department of Human Services; hospital emergency presentations and hospital admissions; sentinel general practitioner surveillance; and medical locum service surveillance. Seasonal trends for influenza and ILI activity were similar for all data sources. Community ILI surveillance, operating as sentinel GP, locum service or hospital emergency department surveillance, in conjunction with notification of laboratory-confirmed influenza, would provide adequate inter-pandemic surveillance for influenza in Victoria and, by extension, in any Australian jurisdiction. Other surveillance systems would be needed for early pandemic case or cluster detection, while pandemic monitoring would be better achieved by a more automated system.