Weekly influenza update, week 50, December 2017
ECDC and WHO/Europe publish weekly influenza surveillance data in the report Flu News Europe.
- Influenza activity was increasing in countries in Western Europe, Scandinavia and Turkey.
- Both influenza types A and B viruses were common and mixed patterns were observed across the Region.
- Of the individuals sampled, on presenting with ILI or ARI to sentinel primary healthcare sites, 26% tested positive for influenza viruses, significantly higher compared to previous weeks.
- Data from 19 countries or regions reporting to the EuroMOMO project indicated that all-cause excess mortality was within normal ranges for this time of year.
2017/18 season overview
An early risk assessment based on data from EU/EEA countries was published by ECDC on 20 Dec 2017. First detections indicated circulation of A(H3N2) and B/Yamagata viruses in the highest proportions. As the A(H3N2) subtype dominated last season, a high proportion of the population should be protected.
From sentinel sources, a slightly higher proportion of type B viruses compared to type A viruses has been detected. Approximately equal proportions of A(H1N1)pdm09 and A(H3N2) viruses have been detected.
For type B viruses from both sentinel and non-sentinel sources, B/Yamagata lineage viruses have greatly outnumbered those of the B/Victoria lineage.
- While low in number, 61% of the genetically characterized A(H3N2) viruses belonged to clade 3C.2a, the vaccine virus clade as described in the WHO recommendations for vaccine composition for the northern hemisphere 2017–18, and 39% to clade 3C.2a1, the viruses of which are antigenically similar to those of clade 3C.2a.
- The Norwegian Institute of Public Health has published an early risk assessment for the influenza season 2017/18 in Norway. See full report here.
- Influenza activity in the United States has been increasing since the beginning of November. Influenza A viruses have been the most commonly identified, with influenza A(H3N2) viruses predominating. See full report here.
- Additional information on global influenza activity is available from WHO’s biweekly global updates.
See all weekly influenza updates
More about influenza surveillance
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
Surveillance reports and disease data on seasonal influenza
Surveillance reports and data: Disease data from ECDC Surveillance Atlas, Annual Epidemiological Reports, Surveillance reports.Read more