Weekly influenza update, week 13, March 2018
In collaboration with WHO Regional Office for Europe, ECDC monitors and reports on influenza activity in Europe on a weekly basis throughout the flu season.
- Influenza viruses continued to circulate in the Region, while all countries reported low or medium intensity of activity of respiratory infections.
- Influenza continued to circulate widely in the Region with 35% of the individuals sampled from primary healthcare settings testing positive for influenza viruses.
- Both influenza virus types A and B were co-circulating with the majority being type B viruses and the B/Yamagata lineage continuing to dominate.
- 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
- Influenza has been circulating widely in the Region since week 52/2017, based on positivity rates among sentinel specimens, which is longer than in previous seasons and may contribute to the severity of the season.
- 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. the Russian Federation, Kazakhstan). 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 characterized A(H3N2) viruses belong to clade 3C.2a and 49% of B/Victoria lineage 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 have occurred in persons above the age of 15 years. Click here for more information
- Mortality from all causes based on pooled data from 18 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. Click here for more information
- A seasonal reassortant A(H1N2) influenza virus consisting of HA and NS genes of human seasonal A(H1N1)pdm09 influenza virus and M, NA, NP, PA, PB1 and PB2 genes of human seasonal A(H3N2) influenza virus was detected in the Netherlands in March. WHO assesses the risk posed by this virus to be comparable to the risk posed by the currently circulating seasonal influenza viruses, as all the genes of this reassortant virus originate from circulating seasonal viruses. Click here for more information
See all weekly influenza updates
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