Via Flu News Europe:
Week 4/2017 (23 - 29 January 2017)
• Influenza activity remained elevated across the region with 28 of 43 countries reporting increased activity.
• Most countries reported stable or decreasing activity compared to the previous week.
• Excess all-cause mortality has been observed among the 15-64 years and 65 years and over age groups in many of the 18 countries that provide data on excess all-cause mortality and, most likely, this is mainly due to the circulation of influenza A(H3N2) virus.
• The proportion of influenza virus detections among sentinel surveillance specimens was 51%, similar to that seen since week 51/2016.
• The great majority of influenza viruses detected were type A (95%) and, of those subtyped, 97% were A(H3N2).
• Most of the hospitalized laboratory-confirmed influenza cases reported have occurred in people aged 65 years or older.
• Influenza activity started early this season compared to previous seasons.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 might be expected to be the most severely affected. Indeed, confirmed cases of influenza virus type 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 virus. While about two-thirds of the A(H3N2) viruses genetically characterized belong to a new genetic subclade (3C.2a1), those that have been antigenically characterized are similar to the vaccine virus (clade 3C.2a).
• Early monitoring of vaccine effectiveness in Finland and Sweden suggests levels of effectiveness in persons aged 65 years and older similar to estimates from annual multi-country studies between the 2011–2012 and 2014–2015 seasons. Given typically suboptimal vaccination coverage and the partial effectiveness of influenza vaccines, rapid use of neuraminidase inhibitors (NAIs) for laboratory-confirmed or probable cases of influenza infection should be considered for vaccinated and non-vaccinated patients at risk of developing complications.
• Reduced susceptibility to Zanamivir has been observed for only one of the tested viruses so far this season.
• A risk assessment on seasonal influenza in EU/EEA countries was published by ECDC on 24 December 2016 and was updated on 25 January 2017. The above description is in line with the findings of these assessments.