A second type of bird flu has been detected among dairy cows in the United States, the U.S. Department of Agriculture’s Animal and Plant Health Inspection Service (APHIS) has reported.
A broad subtype of bird flu called H5N1 has been circulating among U.S. dairy cows since at least 2024. The first cases were detected in cattle in March of last year, and since then, nearly 960 herds across the nation have been affected. That’s according to the latest numbers available on the Centers for Disease Control and Prevention (CDC) website.
The H5N1 virus has a complex family tree, and cows in the U.S. have so far been infected by a branch of that tree known as the B3.13 genotype of clade 2.3.4.4b. Meanwhile, another genotype, called the D1.1 genotype, has been spreading in wild birds and poultry in the U.S. and Canada.
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