Influenza virus characterization: summary report, Europe, September 2022

Overview

This is the ninth and final report for the 2021-2022 influenza season. The July 2022 characterisation report1, gave a breakdown of influenza detections across the World Health Organisation (‎WHO)‎ European Region reported to TESSy up to week 30/2022. As of week 39/2022, 149 372 detections had been reported, resulting from extended late season influenza activity. Of these 149 372 detections, 98% were type A viruses, with A(‎H3N2)‎ dominating (‎91%)‎ over A(‎H1N1)‎pdm09 (‎9%)‎, and 2% type B of which only 156 were ascribed to a lineage, with all but two being B/Victoria. This represents a large increase (‎148 096, 117-fold )‎ in detections compared to the 2020-2021 season, on the back of a great increase (‎1 957 744, 151%)‎ in the number of samples tested. However, while there have been clear indications of an influenza epidemic in 2021-2022 with the epidemic threshold of 10% positivity within sentinel specimens having been crossed for 17 weeks (‎unlike in 2020-2021)‎, numbers of detections are reduced compared to earlier seasons (‎e.g., 9.4% reduced compared to 2019-2020, when the number of samples tested was over 3-fold lower)‎. The increased testing but reduced number of influenza detections is undoubtedly related to the emergence of SARS-CoV-2 and measures introduced to combat it.