As a result of anti-COVID measures, the human influenza virus essentially disappeared globally for the duration of the 2020-2021 flu season.
There has been some concern that, as a result of relaxed anti-COVID measures and a year's worth of missed immunity, the flu may make a more severe resurgence this year.
The US Centers for Disease Control, for example, advises,
Reduced population immunity due to lack of flu virus activity since March 2020 could result in an early and possibly severe flu season.
The WHO-coordinated Global Influenza Surveillance and Response System (GISRS) tallies surveillance samples of influenza from a global network of laboratories. In recent flu seasons, they have reported† peak weekly positive sample counts of 52981 (week 6 of 2019), 51029 (week 5 of 2020), and 456 (week 1 of 2021) in the Northern Hemisphere.