Flu News Europe

Week 2/2017 (9 – 15 January 2017)

• Influenza activity remained widespread across the region with high or very high intensity in 8 out of 44 reporting countries or regions and medium intensity in 26 countries.
• The proportion of influenza virus detections among sentinel surveillance specimens was 46%, a slight decline from 52% in the previous week.
• The great majority of influenza viruses detected were type A (97%) and, of those subtyped, 99% were A(H3N2).
• Most of the hospitalized laboratory-confirmed cases reported have occurred in people aged 65 years or more.
• Excess all-cause mortality among the elderly has been observed in the past 1 to 2 months in most of the 18 countries that take part in  EuroMOMO.

Season overview

• Influenza activity started early this season compared to previous seasons.
• Week 46/2016 is the earliest week that the overall influenza-positivity rate in sentinel specimens reached 10% since the emergence of A(H1N1)pdm09 viruses in the 2009 season; during the last 6 seasons this occurred between weeks 48 and 51.
• Since week 40/2016, influenza A viruses have predominated, accounting for 96% of all sentinel detections; the great majority (99%) of subtyped influenza A viruses from sentinel sites has been A(H3N2).
• In an influenza season in which A(H3N2) viruses predominate, elderly populations can be expected to be most severely affected. Indeed, confirmed cases of influenza A infection reported from hospitals have predominantly been in adults aged over 65 years.
• So far, circulating A(H3N2) viruses are antigenically similar to the vaccine strain. While about two-thirds of the A(H3N2) viruses characterized belong to a new genetic subclade (3C.2a1), these viruses are antigenically similar to the vaccine strain (clade 3C.2a).
• Early monitoring of vaccine effectiveness in Finland and Sweden suggests levels of effectiveness similar to estimates from multi-country studies during the seasons 2011–2012 to 2014–2015 with 26% (95% CI 22% to 30%) and 24% (95% CI 11% to 34%) vaccine effectiveness, respectively, in persons aged 65 years and older with laboratory-confirmed influenza A. Given the partial effectiveness of influenza vaccines, rapid use of neuraminidase inhibitors for laboratory-confirmed or probable cases of influenza infection should be considered for vaccinated and non-vaccinated patients at risk of developing complications.
• No reduced antiviral susceptibility has been observed among the viruses tested.
• A risk assessment on seasonal influenza in EU/EEA countries was published by ECDC on 24 December 2016. The above summary is in line with the findings of the risk assessment.

 

Figure. Influenza virus detections in sentinel-source specimens by type and subtype, by week and cumulatively