Highly pathogenic avian influenza has been found on dairy herds in Michigan and Idaho, indicating further spread to other U.S. states. At the same time, The Washington Post has reported that a person in Texas is being treated for the illness after coming in contact with dairy cows — the second such case in a human.
The National Veterinary Services Laboratories confirmed the presence of bird flu in the Michigan herd on Friday after the herd had recently brought in cows from Texas. The strain confirmed was similar to those found in Texas and Kansas dairies.
Presumptive positive test results have also been received for additional herds in New Mexico, Idaho, and Texas.
The U.S. Department of Agriculture will share updates if those tests are confirmed positive by the national laboratories. “Federal and state agencies continue to conduct additional testing in swabs from sick animals and unpasteurized clinical milk samples from sick animals, as well as viral genome sequencing, to assess whether HPAI or another unrelated illness may be underlying any symptoms,” the USDA wrote in a news release on Friday.
The human patient who has been confirmed to have HPAI has reported eye redness (consistent with conjunctivitis), as their only symptom, and is recovering. The patient was told to isolate and is being treated with an antiviral drug for flu. This infection does not change the H5N1 bird flu human health risk assessment for the U.S. general public, which Centers for Disease Control and Prevention considers to be low.
It is believed that the strain confirmed in Texas and Kansas herds was introduced by wild birds (H5N1, Eurasian lineage goose/Guangdong clade 2.3.4.4b). Initial testing has not found changes to the virus that would make it more transmissible to humans. While cases among humans in direct contact with infected animals are possible, this indicates that the current risk to the public remains low.
The spread of symptoms within the Michigan cattle herd suggests that HPAI transmission among cattle is possible. The USDA and its partners closely monitor the situation and have advised veterinarians and producers to adhere to strict biosecurity measures.
This includes testing animals before any necessary movements, reducing animal transfers, and isolating sick cattle from the herd. Among the affected dairies, the symptomatic animals have recovered after being isolated, with minimal to no associated deaths reported.
There is no concern regarding the safety of the commercial milk supply since all products undergo pasteurization before reaching the market. Therefore, this situation does not pose a risk to consumer health. Dairies are mandated to send only milk from healthy cows for human consumption.
Milk from affected animals is either diverted or destroyed to prevent it from entering the human food chain. Pasteurization has effectively deactivated bacteria and viruses, including influenza, in milk. Pasteurization is mandatory for any milk intended for interstate commerce. The FDA has long held the view that unpasteurized, raw milk can contain harmful microorganisms that pose significant health risks to consumers. In light of the HPAI detections, the FDA is reminding consumers about the associated risks of consuming raw milk.
The FDA advises against selling milk from potentially affected cows
Due to the limited information on HPAI transmission through raw milk, the FDA advises the industry against producing or selling raw milk or unpasteurized milk cheese products made from cows exhibiting signs of illness, including those infected with or exposed to avian influenza.
The FDA says that they are unaware of any milk or food product from symptomatic cows entering interstate commerce. Furthermore, if milk from symptomatic cows is intended for calf feeding, the FDA strongly recommends heat treatment to eliminate harmful bacteria or viruses, such as influenza. For more information on food safety from the FDA, including details about the sale and consumption of raw milk, click here.
So far, the milk loss resulting from symptomatic cattle has been minimal and is not expected to significantly impact the supply or the price of milk and other dairy products. Additionally, due to increased seasonal production, the U.S. typically has an ample milk supply during the spring months.
In collaboration with state and industry partners, federal agencies encourage farmers and veterinarians to promptly report any cattle illnesses to monitor potential additional cases and minimize the impact and risk to farmers, farmworkers, consumers, and other animals. Producers are advised to consult with their veterinarians to report cattle illnesses and implement enhanced biosecurity measures promptly. More information on biosecurity measures can be found here.
