Australian Influenza Surveillance Report and Activity Updates

The Australian Influenza Surveillance Report and Activity Updates are compiled from a number of data sources, which are used to monitor influenza activity and severity in the community. These data sources include laboratory-confirmed notifications to NNDSS; influenza associated hospitalisations; sentinel influenza-like illness (ILI) reporting from general practitioners; ILI-related community level surveys; and sentinel laboratory testing results.

Page last updated: 17 September 2021

The Australian Influenza Surveillance Report (AISR) is published on a fortnightly basis during the influenza season, typically between May and October. Influenza activity updates may be published outside of the seasonal period.

Australian Influenza Surveillance Report - 2021 Influenza Season in Australia

Australian Influenza Surveillance Report No 12 - fortnight ending 12 September 2021

Key Messages

It is important to note that due to the COVID-19 epidemic in Australia, data reported from the various influenza surveillance systems may not represent an accurate reflection of influenza activity. Results should be interpreted with caution, especially where comparisons are made to previous influenza seasons. Interpretation of influenza activity data from April 2020 onwards should take into account, but are not limited to, the impact of social distancing measures, likely changes in health seeking behaviour of the community including access to alternative streams of acute respiratory infection specific health services, and focussed testing for COVID-19 response activities. Current COVID-19 related public health measures and the community’s adherence to public health messages are also likely having an effect on transmission of acute respiratory infections, including influenza.

Activity

  • Following historically low activity levels observed from April 2020 onwards, community influenza-like-illness (ILI) activity in the year to date in 2021 remains at low levels.
  • Notifications of laboratory-confirmed influenza have also remained low since April 2020. In the year to date in 2021, there have been 512 notifications to the National Notifiable Diseases Surveillance System (NNDSS) in Australia, of which 26 notifications had a diagnosis date this fortnight.

Severity

  • There is no indication of the potential severity of the 2021 season at this time.
  • In the year to date, of the 512 notifications of laboratory-confirmed influenza, no influenza-associated deaths have been notified to the NNDSS.
  • There has been one hospital admissions due to influenza reported across sentinel hospitals sites since commencement of surveillance in April 2021.

Impact

  • Given the low number of laboratory-confirmed influenza notifications, low community ILI activity, and low number of hospitalisations due to influenza at sentinel hospital sites, it is likely there is minimal impact on society due to influenza in 2021 to date.

At-risk populations

  • In 2021 to date, adults aged 80-84, adults aged between 60-64 and 65-69, and children under 5 years of age, have the highest influenza notification rates.

Virology

  • To date, 68.4% of notifications of laboratory-confirmed influenza to the NNDSS were influenza A, of which 96.9% were influenza A(unsubtyped) and 3.1% were influenza A(H3N2). Influenza B accounted for 21.3% of notifications, 3.5% were influenza A and B co-infection, 0.4% were influenza C, and 6.4% were untyped.

Vaccine match and effectiveness

  • Of the 20 samples referred to the WHOCC to date, the 1 influenza B/Victoria sample and 1 influenza A(H1N1) sample were characterised as antigenically similar to the corresponding vaccine components, while the 18 influenza A(H3N2) samples were characterised as antigenically dissimilar.
  • The low case numbers of influenza across all systems in the season to date precludes meaningful analysis to estimate vaccine effectiveness for this season.

Full Report

Data considerations

The AISR aims to increase awareness of influenza activity in Australia by providing an analysis of the various surveillance data sources throughout Australia. While every care has been taken in preparing this report, the Commonwealth does not accept liability for any injury or loss or damage arising from the use of, or reliance upon, the content of the report. Delays in the reporting of data may cause data to change retrospectively. For further details about information contained in this report please refer to the AISR 2020 Data Consideration:

Influenza vaccine efficacy, effectiveness and impact explained

There are three general terms that are used to describe how well a vaccine works in any given influenza season: vaccine efficacy, vaccine effectiveness and vaccine impact. This document provides a general explanation of each of these terms as well as information specific to influenza vaccines.

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Previous Reports and Updates

State and Territory Surveillance Reports

For further information regarding current influenza activity at the jurisdictional level, please refer to the following State and Territory departments of health surveillance reports:

Annual Reports

National Influenza Surveillance Scheme

This paper provides a comprehensive summary and analysis of the National Influenza Surveillance Scheme, including surveillance systems that function outside of the Scheme, in 2015. The Scheme is coordinated by the Australian Government Department of Health and supported by a number of surveillance systems that aim to be nationally representative and monitor important aspects of severity, incidence and virology. Influenza activity monitored through its systems is presented in reports available on this page. Several jurisdictionally based surveillance systems that operate outside of the Scheme are used to inform local influenza activity trends. This paper describes the strengths and limitations of these influenza surveillance systems in terms of the aspects of influenza activity that they inform  and their contribution to the overall monitoring of influenza activity in Australia.

Accessibility Issues

Should you encounter issues in accessing the information contained either on this webpage or within the downloadable full reports please email flu (flu@health.gov.au) or contact the Department of Health switchboard on 02 6289 1555 or 1800 020 103.

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