Multiple independent introductions of highly pathogenic avian influenza H5 viruses during the 2020-2021 epizootic in France

During winter 2020-2021, France and other European countries were severely affected by highly pathogenic avian influenza H5 viruses of the Gs/GD/96 lineage, clade 2.3.4.4b. In total, 519 cases occurred, mainly in domestic waterfowl farms in Southwestern France. Analysis of viral genomic sequences indicated that 3 subtypes of HPAI H5 viruses were detected (H5N1, H5N3, H5N8), but most French viruses belonged to the H5N8 subtype genotype A, as Europe. Phylogenetic analyses of HPAI H5N8 viruses revealed that the French sequences were distributed in 9 genogroups, suggesting 9 independent introductions of H5N8 from wild birds, in addition to the 2 introductions of H5N1 and H5N3.

Automated summary

During winter 2020-2021, France and other European countries experienced severe impacts from highly pathogenic avian influenza viruses, predominantly in domestic waterfowl farms. The analysis of viral genomic sequences revealed the presence of three subtypes, with the majority belonging to the H5N8 subtype in France.