Weekly influenza update, week 10, March 2018

Data Graph Map
Period: 05 Mar 2018 - 11 Mar 2018

Influenza viruses continue to circulate widely in the Region, apart from some eastern European countries that have only recently reported increased activity. Similar to the previous week, 50% of the individuals sampled from primary healthcare settings tested positive for influenza virus, despite the peak rate for the Region occurring in week 05/2018. Both influenza virus types A and B were co-circulating with a higher proportion of type B viruses and with B/Yamagata continuing to be the dominant lineage. Similar proportions of influenza type A and B viruses were reported in patients admitted to ICU, while the majority of severe cases reported this season have been due to influenza type B and occur in persons above the age of 15 years.

Influenza in Europe, week 10, 2018

Download

Thumbnail

Summary

  • Influenza viruses continue to circulate widely in the Region, apart from some eastern European countries that have only recently reported increased activity.
  • Similar to the previous week, 50% of the individuals sampled from primary healthcare settings tested positive for influenza virus, despite the peak rate for the Region occurring in week 05/2018.
  • Both influenza virus types A and B were co-circulating with a higher proportion of type B viruses and with B/Yamagata continuing to be the dominant lineage.
  • Similar proportions of influenza type A and B viruses were reported in patients admitted to ICU, while the majority of severe cases reported this season have been due to influenza type B and occur 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.
  • 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.
  • 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 were reported than A(H1N1)pdm09 viruses.
  • While low in number, 57% 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.
  • The majority of severe cases reported this season are due to influenza type B and occur in persons above the age of 15 years.
  • Mortality from all causes from data pooled across 17 EU countries and regions that reported to euroMOMO (http://www.euromomo.eu/) remains elevated in some countries, while it is declining in others.
  • Interim results from 5 European studies indicate that influenza vaccine effectiveness was estimated to be similar to that in recent years.