fluTAS 2012

fluTAS 2012

Reports

Summary of influenza in Tasmania 2012

fluTAS Report 2012

Strains

The pattern of influenza in Tasmania during 2012 was characterised by a single wave of predominately Influenza A H3N2. Influenza B occurred at lower levels during the season. Little disease was due to Influenza A H1N1.

The 2012 seasonal influenza vaccine was based on strains of Influenza A H1N1, Influenza A H3N2 and Influenza B. The strain of Influenza A H3N2 ("Victoria-like") that circulated in the community in 2012 differed slightly from the particular strain of Influenza A H3N2 ("Perth-like") used in the vaccine. The level of "herd immunity" to circulating influenza in Tasmania depends on both past experience of influenza infection, and recent vaccination. This drift in the circulating strain of Influenza A H3N2 in 2012 may have contributed to the prominence of this strain and the age distribution of cases

Notifications

There were more notified influenza cases in Tasmania in 2012 than in 2011. While there was significantly more influenza testing performed during 2012 than in 2011, a higher proportion of influenza PCR tests were positive. This suggests there was truly more influenza in the Tasmanian community in 2012 than in 2011. This is supported by higher levels of influenza-like illness reported by syndromic surveillance systems during 2012 than in 2011.

Season analysis

The number of notified cases in 2012 was greater than the pre-pandemic years 2007 and 2008, and post-pandemic years 2010 and 2011. It was not as large as the pandemic year 2009. These years are probably useful comparators, but the interpretation of surveillance data is complicated as:

  • the strains of influenza virus circulating, and levels of herd immunity to these, vary each year,
  • influenza surveillance activities have increased since 2009,
  • the behaviour of doctors and persons with influenza-like illness may have changed due to heightened awareness of influenza.

During 2012 the peak in influenza like illness reporting, influenza testing, and influenza notifications all occurred during July and August.

With this slightly longer-term perspective in mind, and based upon notifications, testing effort and syndromic surveillance systems, the 2012 Tasmanian influenza season appeared to be more extensive than most recent non-pandemic years.

 About fluTAS

The fluTAS Report is a regular influenza season update to inform healthcare organisations and the public about the current level of influenza disease activity in Tasmania.

Multiple data sources are used to obtain some measure of influenza disease activity in the community.

To provide feedback on the fluTAS Report, email the Communicable Disease Prevention Unit 

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