Higher than normal seasonal influenza activity in Victoria, 2003.

Influenza surveillance in Victoria comprises surveillance of patients with influenza-like illness (ILI) from sentinel general practices and laboratory based reporting of influenza detections, predominantly from hospital inpatients. Surveillance of patients with ILI seen by the Melbourne Medical Locum Service (MMLS) was conducted for the first time in 2003, when the influenza season was characterised by a late onset with higher than normal seasonal activity. Influenza A (H3N2) was the predominant circulating influenza virus type, with 99 per cent of sub-typed viruses identified as a drifted strain, A/Fujian/411/2002-like. Sentinel and hospital laboratory surveillance both indicated low levels of circulating influenza A (H1N1) and influenza B. Although the proportion of patients with ILI detected through MMLS surveillance was greater than the proportion from sentinel general practices, the ILI pattern was comparable between the two surveillance systems.