Australian influenza report 2013—28 September to 11 October 2013 (#09/2013)

The Australian Influenza Report is compiled from a number of data sources, including laboratory-confirmed notifications to NNDSS, sentinel influenza-like illness reporting from General Practitioners and Emergency Departments, workplace absenteeism, and laboratory testing. Reports are produced fortnightly from May to October. A more in-depth end-of-season report is also published in Communicable Diseases Intelligence.

Page last updated: 28 October 2013

Current Report Summary

  • Nationally, influenza activity continued to decrease this fortnight. Influenza activity in Tasmania is currently reported as wide-spread whereas all other jurisdictions are reporting either unchanged or decreasing activity compared to the previous fortnight.
  • As at 11 October 2013, there have been 22,983 cases of laboratory confirmed influenza reported, which is slightly more than half of the notifications received for the same period in 2012.
  • Over the 2012-13 inter-seasonal period, higher than usual numbers of influenza notifications were reported from most jurisdictions. The seasonal increase in influenza notifications commenced in early July and persisted over a shorter period than 2011 and 2012. The season peak of weekly notifications was similar to 2011 and occurred at the end of August.
  • Influenza activity peaked at the end of August in the majority of jurisdictions. Tasmania and the Northern Territory experienced a late peak while Western Australia reported extended increased activity from mid-August through September.
  • Nationally influenza A was the predominant influenza virus type. Influenza A(H1N1)pdm09 re-emerged this season and represented over 15% of overall notifications, compared to <1% of notifications in 2012. Additionally, the proportion of influenza B this season has been higher than in recent years.
  • Across jurisdictions, the distribution of influenza types and subtypes has been variable. In Victoria there was a predominance of influenza type B throughout the season, with all other jurisdictions reporting mostly influenza A. In Western Australia, influenza A(H3N2) was the predominant subtype, whereas New South Wales and other eastern jurisdictions reported mostly A(H1N1)pdm09. Towards the end of the season while the proportion of influenza B remained stable nationally, increases were observed in New South Wales, South Australia and Queensland and the proportion of A(H1N1)pdm09 increased in Western Australia.
  • Notification data show that there was a predominance of influenza B infections in those aged less than 15 years, with influenza A infections most prevalent in the 0-4 and 30-34 years age groups. Consistent with A(H1N1)pdm09 dominated years, there were very few notifications of this subtype in those aged 65 years and over.
  • The rate of influenza associated hospitalisations has started to decline over the past fortnight. Both the 2012 and 2013 influenza seasons saw around 12% of influenza cases admitted directly to ICU with a high proportion of cases had known medical co-morbidities reported. In Australia it has been estimated that there have been over 4,500 influenza associated hospitalisations since April 2013. The age distribution of hospital admissions shows a peak in the 0-9 year age group as is typical of seasons with high levels of influenza B circulating.
  • The WHO has reported that influenza activity has continued to decline in all temperate countries of the southern hemisphere, while influenza-like illness has started to increase in many European countries. Seasonal influenza transmission has not yet been detected in the northern temperate zone.
  • The Australian Influenza Vaccine Committee (AIVC) agreed to adopt the WHO recommendations for the composition of the 2014 southern hemisphere influenza season vaccine. This recommendation is consistent with the WHO recommendations made for vaccines relating to the 2013/14 northern hemisphere season.
  • This will be the final Australian Influenza Surveillance Report for 2013, unless unusual activity becomes apparent over the summer months.

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