The Australian Influenza Surveillance Report is published on a fortnightly basis during the influenza season, typically between May and October. Influenza activity updates will be published outside of the seasonal period, with updates also provided during the season. A more in-depth end-of-season report is also published in Communicable Diseases Intelligence journal.
Australian Influenza Surveillance Report No 10 - 26 September to 09 October 2015
- Nationally, influenza activity has continued to decline following a seasonal peak in mid-August. It is anticipated that influenza activity will decline to inter-seasonal levels in the next few weeks.
- Nationally, and in the Australian Capital Territory, New South Wales, Queensland and South Australia, the season peak of laboratory confirmed notifications of influenza occurred in the week ending 21 August. Notifications peaked one week earlier in Western Australia, while Tasmania and the Northern Territory peaked one and four weeks later, respectively.
- This year children aged less than 15 years accounted for one-third of all influenza notifications, this compares with one-quarter of all notifications in 2014. Notification rates have been highest among those aged between 5 and 9 and over 85 years with a secondary peak in those aged 35-44 years.
- Notably, the 2015 influenza season was characterised by the predominant circulation of influenza B throughout the season. Influenza B viruses accounted for 62% of all notifications this year. Activity was predominately due to B/Yamagata lineage viruses, with B/Victoria lineage viruses increasing towards the end of the season. Where subtype information was available, A(H3N2) was the predominant influenza A subtype with a ratio of approximately 3 notified cases of A(H3N2) for every notified case of A(H1N1). In recent weeks, notifications of influenza A and B have been close to evenly distributed nationally.
- Overall, people experiencing Influenza-like illness (ILI) this year were reported at rates similar to recent years. This season, age-specific rates of ILI were highest in school-aged children. In addition, the rate of ILI in this group was the highest reported in recent years. Historically, influenza has been the primary cause of ILI throughout winter, however this year other respiratory pathogens, including rhinovirus and RSV, continued to circulate.
- Despite the high levels of notifications reported this year, clinical severity appeared less than last year. Presentations to Emergency Departments remained within the range experienced in recent years, however some jurisdictions reported elevated presentations either widespread or regionally at the peak of the season. There were a similar number of hospitalisations reported as last year, however the overall proportion of patients admitted directly to Intensive Care Units (ICUs) was less, at approximately 7%, compared with 10-12% in recent years. Children were admitted to ICU at a slightly higher rate (9%) than adults. Reported mortality was low to moderate and largely limited to the elderly.
- Admissions to ICU due to influenza A and influenza B were reported at similar proportions, suggesting that, at a type level, clinical severity was similar.
- The seasonal influenza vaccines appear to be a good match for circulating strains with 77% of samples matching the trivalent seasonal vaccine (TIV).
- The Australian Influenza Vaccine Committee (AIVC) agreed to adopt the WHO recommendations for the composition of the 2016 southern hemisphere influenza season vaccines.
- This will be the final Australian Influenza Surveillance Report for 2015, unless unusual activity becomes apparent over the summer months.
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Previous Reports and Updates
National Influenza Surveillance Scheme
This paper provides a brief overview of influenza surveillance systems which formed the National Influenza Surveillance Scheme in 2013. The Scheme is coordinated by the Australian Government Department of Health and influenza activity monitored through its systems is presented in reports available on this page. This paper describes the strengths and limitations of surveillance systems in informing the national picture of influenza activity.
For a more detailed description and analysis of the National Influenza Surveillance Scheme, including surveillance systems that function outside of the Scheme, readers are referred to the paper A Review of Influenza Surveillance Systems in Australia, 2013 (Manuscript submitted for publication to Communicable Diseases Intelligence, 22 December 2015).
Should you encounter issues in accessing the information contained either on this webpage or within the downloadable full reports please email flu (email@example.com) or contact the Department of Health switchboard on 02 6289 1555 or 1800 020 103.
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