A(H5N1) spread in North America driven by reassortant lineage turnover
A study published in Science Advances provides a comprehensive phylogenetic and phylogeographic analysis of the North American outbreak of highly pathogenic avian influenza A(H5N1), which was introduced in late 2021. By sequencing 2,955 viral genomes and integrating previously published data, the researchers reached the following main conclusions:
-The A(H5N1) outbreak resulted from multiple introductions and rapid diversification, with successive lineage replacements driven by reassortment events that enhanced viral fitness.
-The virus spread extensively through wild bird migration, affecting over 80 wildlife species and more than 180 million domestic birds across North America.
-Genetic reassortment with local low-pathogenic strains and host shifts contributed to its ongoing dissemination.
These findings emphasize the importance of continued genomic surveillance, particularly in wild birds and mammals, to inform control measures and mitigate risks to both animal and human health.
There is no doubt that the hesitant response to the events in the U.S. significantly contributed to the spread and rapid evolution of the virus.
