Weekly influenza update, week 11, March 2018

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Period: 12 Mar 2018 - 18 Mar 2018

Influenza viruses continue to circulate widely in the Region with some eastern European countries that have only recently reported increased activity, experiencing a late start to the season with increased circulation of influenza type A viruses. Similar to the previous week, 44% of the individuals sampled from primary healthcare settings tested positive for influenza viruses, despite the peak rate for the Region occurring in week 05/2018. Both influenza virus types A and B were co-circulating with the majority being type B viruses and B/Yamagata continuing to be the dominant lineage. Similar proportions of influenza type A and B viruses were reported in patients admitted to ICU, with the majority of severe cases reported this season being due to influenza type B and occurring in persons above the age of 15 years.

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Summary

  • Influenzs viruses continue to circulate widely in the Region with some eastern European countries that have only recently reported increased activity, experiencing a late start to the season with increased circulation of influenza type A viruses.

  • Similar to the previous week, 44% of the individuals sampled from primary healthcare settings tested positive for influenza viruses, despite the peak rate for the Region occurring in week 05/2018.

  • Both influenza virus types A and B were co-circulating with the majority being type B viruses and B/Yamagata continuing to be the dominant lineage.

  • Similar proportions of influenza type A and B viruses were reported in patients admitted to ICU, with the majority of severe cases reported this season being due to influenza type B and occurring in persons above the age of 15 years.

2017/18 season overview 

  • For the region overall, the majority of influenza viruses detected were type B, representing a high level of circulation of influenza B viruses compared to recent seasons. B/Yamagata lineage viruses have greatly outnumbered those of the B/Victoria lineage. Click here for more information

  • Different patterns of dominant type and A subtypes were observed between the countries of the Region, which may be due to differences in relative weights of information being derived from sentinel, non-sentinel and severe influenza case sources of information. Influenza A viruses are dominant in several eastern European countries (e.g. Russian Federation, Kazakstan). See the maps below for more information

  • Of the type A virus detections from sentinel sources, the majority of which were subtyped, A(H1N1)pdm09 viruses have outnumbered A(H3N2) viruses. In non-sentinel sources, more A(H3N2) viruses than A(H1N1)pdm09 viruses were reported. Click here for more information

  • While low in number, 56% of A(H3N2) viruses belong to clade 3C.2a and 48% of B/Victoria viruses belong to a subclade of clade 1A viruses that are antigenically distinct from the current trivalent vaccine component. Click here for more information
  • The majority of severe cases reported this season are due to influenza type B and occur in persons above the age of 15 years. Click here for more information
  • Mortality from all causes based on pooled data from 19 EU countries and regions that reported to EuroMOMO (http://www.euromomo.eu/)remained elevated in some countries, while it was declining in others.  Click here for more information
  • Interim results from 5 European studies indicate that influenza vaccine effectiveness was estimated to be similar to that in recent years. 

See all weekly influenza updates

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