The United States Food and Drug Administration (FDA) announced on Tuesday that samples of pasteurized milk have tested positive for remnants of the bird flu virus that has affected dairy cows. The agency emphasized that the material is inactivated and does not represent actual virus that may pose a risk to consumers.
The detection comes nearly a month after an avian influenza virus, which has caused widespread illness among wild and commercial birds in recent years, was identified in dairy cows in at least eight states. The Agriculture Department reports that 33 herds have been affected to date.
FDA officials did not disclose the number or source of the tested samples. They explained that the agency has been evaluating milk during processing and from grocery stores, with additional test results anticipated in the coming days to weeks.
The FDA utilized a PCR lab test, which can detect viral genetic material even after live virus is eliminated through pasteurization. Dr. Lee-Ann Jaykus, an emeritus food microbiologist and virologist at North Carolina State University, noted that there is no evidence of infectious virus present and that the FDA is monitoring the situation closely.
Previously, the FDA and the USDA assured the public that milk from infected cattle would not enter the commercial supply, as it is required to be diverted and destroyed. Federal regulations mandate pasteurization for milk entering interstate commerce.
The FDA acknowledges that studies on the effects of pasteurization on the bird flu virus in dairy cattle have not been conducted due to the recent nature of its detection. However, previous research indicates that pasteurization is highly effective in inactivating heat-sensitive viruses like H5N1.
Matt Herrick, a spokesperson for the International Dairy Foods Association, emphasized that the time and temperature regulations for pasteurization ensure the safety of the commercial U.S. milk supply. He stated via email that remnants of the virus have no impact on human health.
The confirmation of the H5N1 virus in dairy cows in March followed weeks of reports about a mysterious illness affecting cows in Texas. Symptoms included lethargy and a sharp decline in milk production. Experts indicate that while the H5N1 virus is deadly to commercial poultry, most infected cattle tend to recover within two weeks.
To date, two individuals in the United States have contracted bird flu. A Texas dairy worker in close contact with an infected cow recently developed a mild eye infection but has since recovered. In 2022, a prison inmate working at a Colorado poultry farm became infected while culling infected birds. His only symptom was fatigue, and he also recovered.
