AISR fortnightly report no. 12 – 23 September to 6 October 2019
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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.
Currently, influenza and influenza-like illness (ILI) activity is lower than average for this time of year compared to previous years, and is consistent with past activity following a peak in notifications and coming to the end of the influenza season. At the national level, notifications of laboratory-confirmed influenza have decreased in the past fortnight.
Impact for the season to date, as measured through the number of sentinel hospital beds occupied by patients with influenza and the rate of Flutracking respondents absent from normal duties, is low to moderate.
Clinical severity for the season to date, as measured through the proportion of patients admitted directly to ICU, and deaths attributed to influenza, is low.
The majority of confirmed influenza cases reported nationally were influenza A in the year to date (76.9%) and past fortnight (61.9%). The proportion of cases attributed to influenza B has decreased slightly in the past fortnight.
Vaccine match and effectiveness
Antigenic analysis of circulating influenza viruses in Australia in 2019 shows that the influenza A(H1N1)pdm09 and influenza B/Yamagata-lineage viruses are well matched to the 2019 influenza vaccine while some A(H3N2) and B/Victoria-lineage viruses are less well matched. Overall vaccine effectiveness appears good and as expected based on preliminary estimates from general practice (ASPREN) and sentinel hospitals (FluCAN-PAEDS), noting that effectiveness typically ranges from around 40-60% each year.