High proportion of influenza B characterises the 2008 influenza season in Victoria.

The 2008 influenza season in Victoria was distinctive because of the increased proportion of influenza-like illness (ILI) cases due to influenza B infection and the lateness of the season compared with preceding years. Influenza activity fell within the bounds of normal seasonal activity thresholds. The average rate of ILI reported by general practitioners participating in sentinel surveillance was 5.5 cases per 1,000 consultations, peaking at 13.4 cases per 1,000 consultations. The average ILI rate reported by the Melbourne Medical Deputising Service was 5.1 cases per 1,000 consultations over the season peaking at 16.2 cases per 1,000 consultations at the same time as peak rates were reported by rural geneal practitioners (GPs), with a secondary peak observed 2 weeks later (10.9 cases per 1,000 consultations). Metro GP rates peaked in week 35 (week beginning 25 August) at 15.2 cases per 1,000 consultations. Influenza B cases notified directly to the Victorian Department of Human Services (DHS) from other sources peaked in the 1st week of September with peak numbers of influenza A notifications occurring the following week. Overall 56% of notifications of laboratory confirmed influenza to DHS and 56% of influenza positive swabs from sentinel surveillance were influenza type B.