FDA Is Testing Raw Cow’s Milk Cheese for Avian Influenza

File photo shows bottles of raw milk displayed at a store in Temecula, Calif., on May 8, 2024. JoNel Aleccia/AP Photo

The Food and Drug Administration (FDA) is collecting samples of raw cow’s milk cheese from across the United States to test for the presence of highly pathogenic avian influenza (H5N1), also known as bird flu, the agency said in a Dec. 30 statement.

Sample collection began at the end of December 2024 and is expected to be completed by the end of March 2025, though the collection period could be extended to achieve the FDA’s targets, the agency stated.

Approximately 300 samples of raw cow’s milk cheese—made with unpasteurized milk—will be collected from warehouses and distribution hubs across the country. They will not be taken from retail locations, the FDA said.

The samples will only be collected from cheese that has aged for a minimum of 60 days, which is necessary to mitigate the risk of any pathogens, if present, according to the statement.

Initially, the FDA will test the samples using a PCR test. Any samples indicating the presence of H5N1 will undergo viability testing. The viability testing method is an egg inoculation test developed by the U.S. Department of Agriculture (USDA).

The agency said it will take follow-up actions, if necessary, to address contaminated products and protect consumers.

It also plans to publish its findings on its official website once all testing and analysis are complete.

The FDA has previously warned of the dangers of consuming raw milk, which comes from animals such as cows, sheep, and goats, and has not undergone pasteurization, a heating process that kills both beneficial and harmful bacteria and viruses, including bird flu.

In December, the USDA ordered dairy farmers to work with the department to test raw milk for bird flu amid outbreaks in several states across the country.

Also in December, raw milk and cream products from the company Raw Farm LCC were pulled from shelves in California after testing positive for H5N1.

A total of 66 human cases of H5 bird flu have been reported in the United States since April 2024, according to the U.S. Centers for Disease Control and Prevention. The majority are in California.

To help prevent exposure, health officials are asking people to avoid direct contact with sick or dead animals, particularly wild birds and poultry, and to wear personal protective equipment if contact is unavoidable.

The CDC also advises people not to touch surfaces or materials contaminated with the saliva, mucous, or animal feces of wild or domestic birds or other animals that may be infected with the virus.

In its latest announcement, the FDA said it is working with the CDC, the USDA, and state partners to investigate and respond to the outbreak.

“The FDA’s sampling assignment complements research efforts that the agency is carrying out with its federal and state partners, as well as select research universities,” the agency said. “Unlike the research efforts, the FDA’s sampling assignment is a regulatory activity.”

Bird Flu Mutations

Last month, the CDC said it found mutations in samples taken from a man infected with the first severe case of bird flu in the United States, with the agency noting the mutations were not present in specimens collected from his infected backyard flock.

In a Dec. 26 update, the agency said that an analysis of two respiratory specimens collected from the man—who was previously reported to be older than 65 with underlying health conditions—showed low-frequency mutations in the hemagglutinin (HA) gene, the part of the virus that plays a key role in binding to host cells.

The mutations were not found in poultry samples collected from the man’s property, suggesting the mutations emerged in the patient after he became infected, the CDC said.

Despite the discovery of the mutations, the health agency says the risk to the general public remains low.