AISR – 2019 national influenza season summary
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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.
The 2019 influenza season began earlier compared with recent years. While there was geographic variation across Australia, in general, activity levels in the 2019 influenza season were higher than the 2017 season, but it was a longer season with a smaller peak.
The impact of circulating influenza on society, as measured through the proportion of people with influenza-like illness (ILI) taking time off work, and the burden placed on hospitals with people admitted with influenza, was high.
Clinical severity for the 2019 season, as measured through the proportion of patients admitted directly to intensive care units (ICU), and deaths attributed to influenza, was moderate.
Influenza A(H3N2) predominated nationally, accounting for an estimated 83% of notified laboratory-confirmed cases of influenza in 2019.
Children aged less than 10 years were more commonly infected with influenza; however, the severity of illness in this population was on par with other age-groups.
Vaccine match and effectiveness
Based on available data, vaccinated individuals were 46% less likely to present to a general practitioner (GP) with an ILI and test positive for influenza, and 43% less likely to be hospitalised due to influenza, when compared to unvaccinated individuals.