Bird flu found in Arizona milk suggests another spillover from birds to cows

It appears that there may have been another spillover of H5N1 bird flu virus from wild birds into dairy cattle. The Arizona Department of Agriculture announced Friday that it had found the virus in milk from a herd of cows in Maricopa County, which contains the state capital, Phoenix.

This is the first detection of H5N1 in dairy cows in Arizona, making it the 17th state in which affected cows have been found. Nearly 970 herds have tested positive since the outbreak was first identified in late March 2024.

The Arizona detection occurred as part of the U.S. Department of Agriculture’s National Milk Testing Strategy, which samples bulk milk looking for presence of H5N1 viruses. Last week, USDA and Nevada’s Department of Agriculture announced a detection there of H5N1 in dairy herds. 

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