fluTAS 2011

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fluTAS 2011

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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. 


2011 influenza season summary 

(published December 2011)

The pattern of influenza in Tasmania during 2011 was characterised by the early dominance of the H1N1 strain and then co-circulation with Influenza B at the seasonal peak during mid-winter. The H3N2 strain occurred sporadically throughout the year.

All three influenza strains identified during the year were contained in the 2011 seasonal trivalent influenza vaccine. The level of 'herd immunity' to influenza in Tasmania depends on both past experience of influenza infection, and recent vaccination.

There was an increase in the number of influenza cases notified in Tasmania during 2011 compared with 2010. This may be attributable to a number of factors.

The two influenza 'waves' during 2011 in Tasmania involved an initial wave of Influenza A H1N1 then a later second wave of H1N1 co-circulating with substantially more Influenza B than has occurred in recent years. This second wave was more sustained and involved more cases than the initial wave in 2011, or the single wave during 2010. These characteristics of the 2011 influenza season may have contributed to more cases presenting for medical assessment.

While there was only slightly more influenza testing performed during 2011, more judicious testing may also have contributed to greater confirmation of cases than in 2010.

The number of notified cases in 2011 was similar to the two pre-pandemic years 2007 and 2008. These years are probably useful comparators, but the interpretation of surveillance data is complicated as:

  • there have been changes to influenza virus characteristics (the 2009 pandemic)
  • 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.

With this slightly longer-term perspective in mind, and based upon notifications, testing effort and syndromic surveillance systems, the 2011 Tasmanian flu season appeared to be fairly typical. 

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