Arizona Reports First H5N1 Avian Influenza Detection in Dairy Cattle

The Arizona Department of Agriculture (AZDA), in collaboration with the United States Department of Agriculture (USDA), has confirmed the first detection of H5N1 avian influenza in milk produced by a dairy herd in Maricopa County. As a precautionary measure, the affected facility is currently under quarantine.

Unlike other instances of H5N1 involving the B3.13 strain, cattle in this case have not displayed signs of illness associated with the D1.1 genotype. However, should clinical symptoms emerge, affected cattle will be isolated from the main herd to prevent further transmission.

This detection resulted from AZDA’s implementation of the National Milk Testing Strategy, which began in January and focuses on farm-level bulk tank testing. The identified D1.1 genotype is unrelated to a recent detection of the virus in Nevada and does not exhibit characteristics that would increase the risk of human infection.

Since January, every dairy in Arizona has undergone testing, and so far, only this single facility has returned a positive result.

Authorities emphasize that pasteurized milk and other dairy products remain safe for consumption. The pasteurization process effectively eliminates potential pathogens, including avian influenza.

Ensuring the health and safety of dairy workers and the public is AZDA’s top priority. The agency is working closely with the Arizona Department of Health Services and the Maricopa County Department of Public Health to provide safety guidelines, monitor workers at the affected site, and mitigate the risk of transmission among livestock. While the overall risk to the public remains low, individuals in close contact with dairy cattle may face a higher risk due to their direct exposure to potentially affected animals.