Influenza virus characterization: summary report, Europe, July 2022

Overview

This is the eighth report for the 2021-2022 influenza season.

The June 2022 characterization report gave a breakdown of influenza detections across the World Health Organization (‎WHO)‎ European Region reported to TESSy up to week 25/2022. As of week 30/2022, 145 913 detections had been reported (‎a rise of nearly 13 000 since week 20/2022)‎ resulting from extended late season influenza activity. Of these 145 913 detections, 98% were type A viruses, with A(‎H3N2)‎ still dominating (‎84%)‎ over A(‎H1N1)‎pdm09 (‎16%)‎, but by a lower margin than in the June report (‎92%:8%)‎, and 2% type B of which only 134 were ascribed to a lineage, with all but two being B/Victoria.

This represents a large increase (‎144 903, 144-fold)‎ in detections compared to the 2020-2021 season, on the back of a great increase (‎1 926 053, 176%)‎ 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 as of week 25/2022 (‎unlike in 2020-2021)‎, numbers of detections are reduced compared to earlier seasons (‎e.g., 12% reduced compared to 2019-2020)‎. 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.