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According to a report authored by Dr. Ian H. Brown, Chair of an avian influenza steering committee of the FAO, 41 nations have reported highly pathogenic avian influenza in either wild birds or domestic poultry since May 2021.  Eleven nations in Asia have been affected, 21 in Europe, and nine in Africa.  Isolates conform to the HA Clade 2.3.4.4b.  Most cases in Africa and Europe are caused by H5N1 or H5N8. Asia is impacted by H5N1, H5N2, H5N6, and H5N8.

Since September 2021 there has been an increase in H5N1 outbreaks in Europe.  During September cases occurred in the  Russian Federation, the Czech Republic. Italy and the U.K. reported cases in October with isolates demonstrating similar genotypes with characteristics reminiscent of strains isolated  from cases in Africa during late 2020 and early 2021.

Co-circulation of different H5 lineages in diverse populations of free living birds will lead to evolution by both drift and reassortment.  Fortunately avian epidemiologists can apply genome sequence analysis to monitor the emergence of novel strains including recombinants.

Given the role of free-living birds in transmission and dissemination of H5N1, it is necessary to enhance biosecurity in commercial operations and to maintain surveillance. If vaccination is used as a control measure it is critical to match antigen to the prevalent strain in an affected area.