AISR fortnightly report no. 3 – 25 April to 8 May 2022
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The Australian Influenza Surveillance Report (AISR) is compiled from several data sources 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
- sentinel laboratory testing results.
The AISR is published fortnightly during the influenza season, typically between May and October. Influenza activity updates may be published outside of the seasonal period.
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 2020 influenza activity data 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.
Influenza-like-illness (ILI) activity in the community in 2022 has increased since March following the decrease in activity reported in mid-February.
In the year to date in 2022, there have been 10,599 notifications to the National Notifiable Diseases Surveillance System (NNDSS) in Australia, of which 7,173 notifications had a diagnosis date this fortnight—three times higher than notifications in the previous fortnight.
From mid-April 2022, the weekly number of notifications of laboratory-confirmed influenza reported in Australia has exceeded the 5 year mean.
There is no indication of the potential severity of the 2022 season at this time.
In the year to date, of the 10,599 notifications of laboratory-confirmed influenza, no influenza-associated deaths have been notified to the NNDSS.
There have been 153 hospital admissions due to influenza, including seven ICU admissions, reported across sentinel hospitals sites since commencement of seasonal surveillance in April 2022.
There is no indication of the potential impact of the 2022 season on society at this time.
In 2022 to date, people aged 15–24 years and children aged younger than 10 years have the highest influenza notification rates.
To date, 96.5% of notifications of laboratory-confirmed influenza to the NNDSS were influenza A, of which 91.3% were influenza A(unsubtyped), 2.0% were influenza A(H1N1), and 6.8% were influenza A(H3N2). Influenza B accounted for 0.2% of notifications, and 3.3% were untyped.
Vaccine match and effectiveness
Of the 259 samples referred to the WHOCC to date, all influenza A(H1N1) and 98% of influenza A(H3N2) samples were characterised as antigenically similar to the corresponding vaccine components, while the influenza B/Victoria sample was characterised as antigenically dissimilar.
It is too early to assess vaccine match and effectiveness for this season.