Weekly influenza update, week 16, April 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 activity was at inter-season levels in all but one reporting country.
- While low in number, 12% of the individuals sampled from primary healthcare settings tested positive for influenza viruses (compared to 23% in the previous week).
- Both influenza virus types A and B were co-circulating with the majority being type A.
2017/18 season overview
- Influenza viruses have been circulating widely in the Region between weeks 52/2017 and 16/2018 (based on increased proportions - 10% and above - of sentinel specimens testing positive for influenza viruses). This is longer than in recent seasons and may contribute to the severity of this 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.
- Different patterns of dominant type and A subtypes were observed between the countries of the Region.
- 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, similar numbers of A(H3N2) viruses and A(H1N1)pdm09 viruses were reported.
- While low in numbers, characterized A(H3N2) viruses fell mainly in clade 3C.2a (57%) and subclade 3C.2a1 (42%), while 42% of B/Victoria lineage viruses fell in a subclade of clade 1A viruses that are antigenically distinct from the current trivalent vaccine component.
- The majority of severe cases reported this season were due to influenza virus type B infection and have mostly occurred in persons older than 15 years.
- Mortality from all causes now appears be have returned to normal expected levels in all 21 participating countries and regions that report to EuroMOMO.
- Interim results from 5 European studies indicate 25 to 52% vaccine effectiveness against any influenza.
Seasonal influenza is a preventable infectious disease with mostly respiratory symptoms. It is caused by influenza virus and is easily transmitted, predominantly via the droplet and contact routes and by indirect spread from respiratory secretions on hands etc.Read more
European Influenza Surveillance Network (EISN)
The network combines epidemiological and virological surveillance of influenza.Read more