The U.S. Department of Agriculture (USDA) has implemented a new federal order to test the nation’s milk supply for the H5N1 bird flu strain, amid growing concerns over its potential to infect humans. This order reflects the urgency of addressing the ongoing outbreak, which has alarmed researchers due to the virus’s ability to mutate into forms that could more easily infect humans. Developed with input from public health, veterinary, and state stakeholders, the new guidance aims to strengthen H5N1 surveillance within the dairy industry.
As part of the new regulations, all entities involved in dairy operations—such as farms, bulk milk transporters, and processing facilities—will be required to provide milk samples upon request for testing. If a herd is found to have infected cattle, owners must also provide epidemiological data to assist with disease surveillance and contact tracing efforts. Additionally, private labs and state veterinarians are obligated to report any positive results from raw milk samples to the USDA.
Testing is set to begin the week of December 16 across six states: California, Colorado, Michigan, Mississippi, Pennsylvania, and Oregon. Though not all these states have reported H5N1 cases in cattle, federal investigators are aiming to identify which herds are affected. Some states are already conducting testing aligned with the new federal order, facilitating a swift and coordinated response to the outbreak.
The broader context of the H5N1 outbreak has included human cases, with Arizona recently confirming its first two cases of bird flu in workers exposed to infected poultry. While both individuals recovered with mild symptoms, the situation underscores the risk of human transmission, with additional cases reported in several other states. The CDC has noted the importance of expanding testing for farm workers and monitoring human infections closely to track the virus’s spread.
Researchers have raised significant concerns about the virus’s potential to mutate and become more efficiently transmissible between humans. A study published in Science highlighted that a single mutation could enable the virus to bind more effectively to human cells, which is a critical step for human-to-human transmission. Though this study did not examine all necessary factors for human transmission, it has intensified fears about the pandemic risk posed by H5N1, prompting more rigorous testing and surveillance efforts at both the animal and human levels.
