The U.S. Food and Drug Administration (FDA) announced on Tuesday that samples of pasteurized milk had tested positive for remnants of the bird flu virus. The agency emphasized that the material is inactivated and that the findings ‘do not represent actual virus that may be a risk to consumers.’ Officials added that they are continuing to study the issue.
The announcement comes nearly a month after an avian influenza virus was detected in dairy cows in at least eight states. The Agriculture Department reports that 33 herds have been affected to date.
FDA officials declined to reveal the number of samples tested or their source, stating that milk is being tested during processing and from grocery stores. Results of additional tests are anticipated ‘in the next few days to weeks.’
Dr. Lee-Ann Jaykus, an emeritus food microbiologist and virologist at North Carolina State University, explained that the PCR lab test used by the FDA can detect viral genetic material even after it has been killed by heat treatment or pasteurization. ‘There is no evidence to date that this is infectious virus and the FDA is following up on that,’ Jaykus said.
Previously, FDA and USDA officials had stated that milk from infected cattle would not enter the commercial supply, as milk from sick animals is required to be diverted and destroyed. Federal regulations mandate pasteurization for milk that enters interstate commerce.
The FDA noted that, while the detection of the bird flu virus known as Type A H5N1 in dairy cattle is new, past research indicates that pasteurization is ‘very likely’ to inactivate heat-sensitive viruses like H5N1.
Matt Herrick, a spokesman for the International Dairy Foods Association, asserted that the time and temperature regulations for pasteurization ensure the safety of the commercial U.S. milk supply. He wrote in an email that remnants of the virus ‘have zero impact on human health.’
The H5N1 virus in dairy cows was confirmed in March, following reports of a mysterious illness affecting cows in Texas. The cows exhibited lethargy and a significant decline in milk production. While the H5N1 virus is fatal to commercial poultry, most infected cattle tend to recover within two weeks, according to experts.
To date, only two people in the U.S. have been infected with bird flu. One individual, who had close contact with an infected cow, developed a mild eye infection and has since recovered. In 2022, a prison inmate contracted the virus while working to kill infected birds at a poultry farm in Colorado; he experienced only fatigue and recovered.
