USDA detects a second bird flu strain in dairy cattle, agency email says

Strain not seen in cows previously

Published: February 5, 2025

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(MartineDoucet/E+/Getty Images)

Reuters — The U.S. Department of Agriculture has detected a bird flu strain in dairy cattle that previously had not been seen in cows, according to an email from the agency’s Animal and Plant Health Inspection Service seen by Reuters.

Before this detection, all of the 957 bird flu infections among dairy cow herds reported this year had been caused by the same strain of the virus, according to the USDA.

The agency on Wednesday said that genome sequencing of milk from Nevada had identified a different strain present in dairy cows for the first time, according to the email.

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That strain was the predominant genotype among wild birds this past fall and winter, the email said. It was identified through the agency’s National Milk Testing Strategy, which began testing milk across the country for bird flu in December.

Reuters could not immediately verify the email with the USDA. The agency did not immediately respond to a request for comment.

The Nevada Department of Agriculture said in a Jan. 31 statement that herds in two counties had been placed under quarantine due to bird flu detections. It did not identify which strain had infected the herds, only that the strain had been detected in wild birds.

The state agency did not immediately respond to a request for comment.

The USDA on January 31 reported four dairy herds in Nevada with bird flu, according to agency data.

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