Australian Influenza Surveillance Report - week ending 29 September 2017 (#10/2017)

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: 06 January 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 10 - week ending 29 September 2017

Summary

  • Influenza activity at the national level continued to decline this reporting fortnight after reaching a peak in mid-August. Despite the national decline, high levels of activity continue to be reported across the country, with seasonal activity in some areas of the country yet to have reached a peak.
  • 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.
  • Moderate levels of influenza activity in the community are likely to continue for the next few weeks as the season returns to baseline levels.
  • 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, further supporting that the season has peaked nationally. 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 a significant cause of ILI in the community.
  • Influenza A(H3N2) is currently the predominant circulating influenza A virus nationally, however influenza B is predominating in a number of jurisdictions and circulating at high levels in many others. The proportion of total notifications attributed to influenza B continued to increase nationally this reporting fortnight.
  • Notification rates this year to date have been highest in adults aged 80 years or 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 predominated.
  • 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 than average influenza activity in the community.
  • Clinical severity for the season to date, as measured through the proportion of patients admitted directly to ICU, and deaths attributed to pneumonia or influenza, is low to moderate. The proportion of 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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