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Understanding avian #influenza #mortality

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By G.M.

 


{Excerpt}

Highly pathogenic avian influenza caused by H5N1 viruses emerged in East Asia in the late 1990s and spread to Europe, Africa, and the Middle East, circulating in wild and domestic birds and occasionally spilling over into mammals and humans. These viruses are classified into genetic lineages called clades based on differences in the gene encoding hemagglutinin, a key surface protein involved in cell entry. In 2021, one such lineage, clade 2.3.4.4b, crossed from Europe to Canada. It spread rapidly, reaching the southern tip of South America in less than 2 years and causing massive mortality in seabirds and marine mammals, including South American sea lions (Otaria flavescens) and southern elephant seals (Mirounga leonina) (1). However, human mortality has been markedly lower in the present H5N1 outbreak than in past ones. If the virus evolves the capacity to transmit from human to human, understanding this reduction will be essential for mounting an effective response.

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