Samples of pasteurized milk on grocery store shelves have tested positive for remnants of the bird flu virus that has already infected herds of dairy cows, the U.S. Food and Drug Administration (FDA) said Tuesday.
The FDA stressed that the material is inactivated and that the findings "do not represent [an] actual virus that may be a risk to consumers." Officials added that they're continuing to study the issue.
Bird flu virus, known as Highly Pathogenic Avian Influenza (HPAI) or H5N1, is a disease that is highly contagious and often deadly in poultry.
Infection with the virus causes decreased lactation, low appetite and other symptoms in affected cattle, the FDA says.
The FDA and U.S. Department of Agriculture (USDA) said that commercial milk supply is safe because of the pasteurization process.
The pasteurization process involves killing harmful bacteria and viruses by heating milk to a specific temperature for a set period of time to make milk safer. Federal regulations require milk that enters interstate commerce to be pasteurized.
"The pasteurization process has served public health well for more than 100 years," the FDA said. "Even if [the] virus is detected in raw milk, pasteurization is generally expected to eliminate pathogens to a level that does not pose a risk to consumer health."
"To date, we have seen nothing that would change our assessment that the commercial milk supply is safe."
Pasteurization is different from complete sterilization, which extends shelf life but is not required to ensure milk safety, the agency said.
Officials with the FDA and the USDA had previously said milk from affected cattle did not enter the commercial supply. Milk from sick animals is supposed to be diverted and destroyed.
FDA officials did not indicate how many samples they tested or where they were obtained. The agency has been evaluating milk during processing and from grocery stores, officials said. Results of additional tests are expected in "the next few days to weeks."
The PCR lab test the FDA used would have detected viral genetic material even after a live virus was killed by pasteurization or heat treatment, Lee-Ann Jaykus, an emeritus food microbiologist and virologist at North Carolina State University told the Associated Press.
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"There is no evidence to date that this is [an] infectious virus and the FDA is following up on that," Jaykus said.
Scientists confirmed the H5N1 virus in dairy cows in March after weeks of reports that cows in Texas were suffering from a mysterious malady.
The FDA says HPAI has now been confirmed in domestic livestock in 33 herds across eight states: Idaho, New Mexico, Texas, South Dakota, Kansas, Michigan, Ohio, and North Carolina.
While the virus is lethal to commercial poultry, most infected cattle seem to recover within two weeks, experts say.
The National Milk Producers Federation (NMPF) echoed the FDA’s assertions that pasteurization is effective against HPAI and that commercial milk supply is safe.
"Viral fragments detected after pasteurization are nothing more than evidence that the virus is dead; they have zero impact on human health," the NMPF said in a statement.
"Further, the federal PMO prohibits milk from sick cows from entering the food supply chain. Milk and milk products produced and processed in the United States are among the safest in the world."
The news comes after a goat in Minnesota tested positive HPAI in February, which marked the first U.S. case of bird flu in domestic cattle, sheep, goats or their relatives.
The positive juvenile goat was residing on a Stevens County farm that already had bird flu infected poultry, according to the Minnesota Board of Animal Health.
To date, two people in the U.S. have been infected with bird flu. A Texas dairy worker who was in close contact with an infected cow earlier this year developed "eye redness" and has recovered, according to the Centers for Disease Control and Prevention (CDC).
In 2022, a prison inmate in a work program caught it while killing infected birds at a Colorado poultry farm. His only symptom was fatigue and he also recovered.
The Associated Press contributed to this report.
