FDA begins testing aged raw cow’s milk cheese samples nationwide for bird flu

(NEW YORK) — Federal health officials have begun collecting samples of aged raw cow’s milk cheese across the U.S. to test for bird flu, the Food and Drug Administration announced.

Sample collection started at the end of this month and is expected to be completed by the end of March 2025, the FDA said Monday. If needed, the agency said it will extend the collection period.

It comes after the U.S. Department of Agriculture issued a federal order earlier this month that raw milk samples nationwide would be collected and shared with the agency to be tested for bird flu.

The FDA said it plans to collect 300 samples of raw cow’s milk cheese that has been aged for at least 60 days from warehouses and distribution centers across the country.

Samples will be tested with a PCR test, which looks for genetic material from the virus, and will be completed within one week of collection, according to the FDA. Samples that indicate the presence of the virus will undergo viability testing.

Viability testing will be done by injecting part of the virus into an embryonated egg and analyzing if it grows or multiplies.

Raw milk cheese is made with unpasteurized milk. In the U.S., cheese can be made from raw milk but must be aged a minimum of 60 days to lessen the risk of any pathogens that may be present, per the FDA.

Samples that test positive for viable virus will be “evaluated on a case-by-case basis,” the FDA said, and the agency may issue actions “such as a recall, follow-up inspection or other possible responses to protect public health.”

The FDA has previously warned of the dangers of drinking raw milk, which does not undergo pasteurization — a process that kills viruses and bacteria. The agency currently considers unpasteurized soft and hard cheeses, as well as other products made from unpasteurized milk, a “high-risk choice.”

Past studies from federal health officials have shown that pasteurization effectively kills the bird flu virus. Nearly all, or 99%, of the commercial milk supply produced on dairy farms in the U.S. follows a national pasteurization program.

Pasteurization has been a practice in the U.S. for more than 100 years and kills harmful bacteria and viruses by heating milk to a specific temperature over time, the FDA notes.

The U.S. has been facing an outbreak of bird flu, or avian influenza, since April, when the first human case was reported.

As of Tuesday, 66 human cases have been confirmed in seven states, according to Centers for Disease Control and Prevention data. California has the highest number of cases with 36.

Almost all confirmed cases have had direct contact with infected cattle or infected livestock. Most bird flu cases in the U.S. have been mild, and patients have typically recovered after receiving antiviral medication.

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