On Feb. 11, 2025, the Arizona Department of Agriculture (AZDA) reported working in conjunction with the United States Department of Agriculture (USDA), confirmed Arizona’s first identified H5N1 avian influenza detection in milk produced by a dairy herd in Maricopa County.

As a protective measure, the facility was under quarantine. Unlike other detections involving B3.13 H5N1, cattle have not yet displayed signs of illness with this particular D1.1, but if clinical symptoms become evident, cattle will be isolated from the main herd.

This detection stemmed from AZDA’s implementation of the National Milk Testing Strategy initiated in January focusing on farm-level bulk tank testing. This detection of avian influenza is consistent with a D1.1 genotype and unrelated to the recent Nevada detection of this virus. This D1.1 genotype bears no features that would make it more likely to infect humans. Every dairy in Arizona has been tested at least once since January; thus far only a sample from this dairy has tested positive. Milk and other dairy products that have been pasteurized are safe to consume.