Higher proportion of older influenza A(H1N1)pdm09 cases in Victoria, 2011

The influenza surveillance system in Victoria is comprised of several components, including a general practitioner sentinel surveillance system, surveillance for influenza-like illness (ILI) in consultations made by the Melbourne Medical Deputising Service, laboratory confirmed influenza notified to the Victorian Department of Health and strain typing performed by the World Health Organization Collaborating Centre for Reference and Research on Influenza. As measured by ILI from both the MMDS and GPSS, the 2011 influenza season in Victoria was mild compared to previous seasons and was not dominated by any type or subtype of influenza. There were 13 laboratory confirmed influenza outbreaks in 2011, nearly all of which were in aged care facilities. GPs continue to swab more patients, a trend started in 2009, with a significantly lower percent of these testing positive for influenza than previous years. The proportion of ILI and swabbed patients who were vaccinated was also significantly lower in 2011 than previously. Strain analysis undertaken by the WHO Collaborating Centre indicated a good antigenic match between the 2011 vaccine and circulating strains. The Victorian influenza surveillance system continues to provide a reliable, consistent system for monitoring the epidemiology of ILI and laboratory confirmed influenza in Victoria.