Australian Influenza Surveillance Report - week ending 13 October 2017 (#11/2017)

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: 24 October 2017

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

Australian Influenza Surveillance Report No 11 - week ending 13 October 2017

Summary

  • Influenza activity at the national level continued to decline this reporting fortnight after reaching a peak in mid-August. With the exception of the Top End in the Northern Territory, influenza activity declined in all regions of the country.
  • Low to moderate levels of influenza activity in the community are likely to continue for the next few weeks as the season returns to baseline levels.
  • The peak week of national influenza activity this season has been at comparable or higher levels than in recent years, with high activity persisting at the peak of the season for a number of weeks.
  • There has been more than two and a half times the number of laboratory confirmed notifications of influenza reported to the National Notifiable Diseases Surveillance System (NNDSS) this year when compared with the same period last year. An earlier season onset and introduction of rapid testing have contributed, in part, to this increase. Administrative backlogs in data entry experienced in some jurisdictions are likely to alter the pattern of notifications once the backlog is resolved.
  • National indicators of influenza-like illness (ILI) continued to decline in the last fortnight and are within historical ranges for this time of year. The proportion of patients presenting to sentinel general practitioners with ILI and testing positive for influenza declined this fortnight but remained at moderate levels, indicating that influenza remains an important cause of ILI in the community.
  • While influenza A(H3N2) was the dominant circulating influenza virus throughout the season, influenza B is currently the dominant circulating influenza virus nationally and in many jurisdictions.
  • Notification rates this year to date have been highest in adults aged 80 years and older, with a secondary peak in young children, aged 5 to 9 years. This is consistent with previous seasons where influenza A(H3N2) and influenza B, respectively, have dominated.
  • Admissions to sentinel hospitals with confirmed influenza decreased this reporting fortnight, following a peak in late August. The large number of admissions this season is consistent with the higher number of cases in the community, and not necessarily reflecting an increase in severity of infection.
  • Clinical severity for the season to date, as measured through the proportion of hospitalised patients admitted directly to ICU, and deaths attributed to pneumonia or influenza, is low to moderate. The proportion of hospitalised patients admitted directly to ICU has been on the lower range reported in recent years. There have been a number of reported deaths due to influenza and pneumonia and the majority have been in the elderly, which is consistent with a season predominated by influenza A(H3N2).
  • To date, based on antigenic characterisation of circulating influenza viruses, the seasonal influenza vaccines appear to be a moderate to good match for circulating virus strains, depending on the strain. Vaccine effectiveness estimates, which provide an indication of how well the vaccine provides protection against influenza, will not be completed until the end of the influenza season.

Full Report

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Previous Reports and Updates

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