Twenty-eight out of 45 Member States in the WHO European Region reported widespread influenza activity based on epidemiological data from surveillance for influenza-like illness (ILI) and acute respiratory infection (ARI).
While seven countries reported high influenza intensity, influenza may have peaked in some parts of the Region as indicated by reports of decreasing trends in 21 countries out of 37 that reported on this indicator.
Thirty-eight countries reported influenza virus detections in 46% of specimens from sentinel sources, indicating influenza activity in the WHO European Region. Influenza B virus constituted 43% of detections in sentinel samples, indicating a gradual shift towards influenza B. Influenza A(H1N1)pdm09 viruses remained the predominant virus detected through sentinel surveillance, accounting for 86% of the A viruses subtyped.
Cases of severe disease were fewer than in previous weeks, but varied between countries. Most severe cases were associated with A(H1N1)pdm09 and were in people aged 15-64 years.
So far, a predominance of influenza A(H1N1)pdm09 viruses has characterized the 2015–2016 influenza season in most countries in the Region; this subtype may cause more severe disease and deaths in people under 65 years than A(H3N2) viruses.
Since week 52/2015, several European countries with sentinel surveillance systems for severe acute respiratory infection (SARI) have reported increasing numbers of cases associated with A(H1N1)pdm09 infection. Similarly, countries reporting laboratory-confirmed influenza cases in hospitals and intensive care units (ICUs) have detected influenza A virus in the majority of cases since the start of the season, with A(H1N1)pdm09 being the dominant subtype.
Most of the viruses characterized so far have been similar to the strains recommended for inclusion in the trivalent or quadrivalent vaccines for this season for the northern hemisphere.
Recommendations for the vaccine composition for the 2016-2017 season in the northern hemisphere are available: including a virus of the B/Victoria lineage in trivalent vaccine is advised.