After identifying remnants of bird flu virus in grocery store milk, federal officials announced Wednesday that they “believe” the nation’s milk supply is safe and that the virus is inactivated by pasteurization.
“Heating milk to a specific temperature for a set period of time through pasteurization is done to limit the activity of pathogens to a level that does not pose a risk to consumer health,” said Don Prater, acting director of the U.S. Food and Drug Administration’s Center for Food Safety and Applied Nutrition.
However, Prater acknowledged that “no studies on the effects of pasteurization on HPAI (high pathogenic avian influenza) viruses and bovine milk have previously been completed.”
Wednesday’s assurance of safety follows a series of bird flu outbreaks in dairy farms in eight states. FDA scientists said they have identified genetic material from the current bird flu strain in samples of pasteurized milk from grocery shelves. The DNA testing done so far was unable to determine conclusively whether the viral particles were active or inactive.
Prater described the situation as novel and evolving but asserted that pasteurization and sterilization have “served public health well for over 100 years.”
And studies done on similar virus types indicate that while pasteurization may not eliminate the virus, it will inactivate it, said Suresh Kuchipudi, professor and chair of the department of infectious disease and microbiology at the University of Pittsburgh’s School of Public Health.
Dawn O’Connell, Health and Human Services assistant secretary for preparedness and response, stressed that the risk to human health is low but that the federal government remains “watchful and ever ready … to keep the American people safe.”
Steve Lyle, a spokesman for the California Department of Food and Agriculture, who was not on the call, said in an email that the federal government was the lead on this, and the state had no additional response or information to share.
Government researchers are actively testing the virus found in milk samples in the laboratory to see whether it grows in either cell cultures or embryonated chicken eggs. These tests, said Jeanne Marrazzo, director of the National Institute of Allergy and Infectious Diseases, will indicate whether the virus is active, or not.
Early tests indicate the virus is not alive.
They are also expanding their surveillance and monitoring and suggested that more information will be released in the days to come.
In addition, they issued a federal order requiring that laboratories report any dairy cattle testing positive for avian flu or any type of influenza A, as well as the testing of all lactating dairy cattle moving between states. In addition, any farm where bird flu positive cows have been discovered will be required to undergo epidemiological investigation and movement tracing, said Mike Watson, administrator for the Animal and Plant Health Inspection Service.
Details on the number of milk samples tested, where they were obtained, and how many of the samples tested positive for the virus were not shared with reporters
Nirav Shah, principal deputy director of the U.S. Centers for Disease Control and Prevention, said the agency has tested 23 people for the virus and are actively monitoring 44 people “who are considered exposed and at risk for infection.”
So far, only one human case has been identified in the current outbreak, and that person was reported to have exhibited only mild symptoms.
In other places where humans have been infected, the virus has made people sicker and has even been lethal. According to the World Health Organization, which has been tracking the virus, between January 2003 and February 2024, there were 887 confirmed cases of human infection across 23 countries. Of those, 462 were fatal.
While the current virus has not developed the ability to become more transmissible to humans, researchers have noted some worrisome mutations.
These include the observations of the virus spreading between cows within the same herd, from cows to poultry, and the movement of the virus between dairies associated with cattle movements. It’s also been detected in cows that didn’t have clinical signs of the disease — suggesting it is moving unnoticed.
In addition, on April 16, a USDA microbiologist “identified a shift” in one sample from McAllen, Kan., that appeared to show a mutation that would make it more transmissible between mammals, said Watson, the USDA official. He said further analyses by the CDC showed “low risk overall.”