AISR fortnightly report no. 9 – 12 August to 25 August 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, overall influenza and influenza-like illness (ILI) activity is lower than average for this time of year compared to previous years, and current activity is consistent with activity in previous years following a peak. At the national level, notifications of laboratory-confirmed influenza continued to decrease in the past fortnight following an apparent peak in early July.
Clinical severity for the season to date, as measured through the proportion of patients admitted directly to ICU, and deaths attributed to influenza, is considered low.
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 considered to be low to moderate.
The majority of confirmed influenza cases reported nationally were influenza A in the year to date (79.5%) and reporting fortnight (70.7%). Of the influenza A cases that were subtyped, there has been a higher proportion of influenza A(H3N2) compared to influenza A(H1N1)pdm09. The proportion of cases attributed to influenza B has increased slightly in the past fortnight, following a steady decline during July.
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 sentinel general practice (ASPREN) and sentinel hospital (FluCAN-PAEDS) surveillance systems, noting that effectiveness typically ranges from around 40-60% each year.