Weekly influenza update, week 18, April/May 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.
- 6% of the individuals sampled from primary healthcare settings tested positive for influenza viruses (compared to 11% in the previous week).
- The number of influenza virus detections has further decreased compared to previous weeks.
2017/18 season overview
- Influenza viruses circulated at high levels in the Region between weeks 52/2017 and 12/2018 (based on increased proportions - 40% and above - of sentinel specimens testing positive for influenza viruses). This is longer than in recent seasons and may have contributed to the severity of this season.
- 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.
- 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 20 participating countries and regions that report to EuroMOMO.
- Interim results from 5 European studies indicate 25 to 52% vaccine effectiveness against any influenza.
See all weekly influenza updates
More about seasonal 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
ECDC publications and peer-reviewed articles on influenza surveillance
ECDC publications and peer-reviewed articles on influenza surveillance.Read more