After identifying remnants of the avian 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 defined period of time through pasteurization aims to limit pathogen activity to a level that does not pose a health risk to consumers,” said Don Prater, director of Acting U.S. Food and Drug Administration. Center for Food Safety and Applied Nutrition.
However, Prater acknowledged that “no studies on the effects of pasteurization on HPAI (highly pathogenic avian influenza) viruses and bovine milk have been done before.”
Wednesday’s safety assurance follows a series of bird flu outbreaks on dairy farms in eight states. FDA scientists say they have identified the genetic material of the current strain of bird flu in samples of pasteurized milk from grocery store shelves. DNA tests carried out so far have not been able to conclusively determine whether the virus particles were active or inactive.
Prater described the situation as new and evolving, but said pasteurization and sterilization “have served public health well for over 100 years.”
Studies done on similar types of viruses indicate that although pasteurization does not eliminate the virus, it will inactivate it, said Suresh Kuchipudi, professor and chair of the department of infectious diseases and microbiology at the School of Public Health. from the University of Pittsburgh.
Dawn O’Connell, assistant secretary for Health and Human Services for preparedness and response, stressed that the risk to human health is low but that the federal government remains “vigilant and ever ready…to ensure safety of the American people.”
California State Veterinarian Annette Jones said there had been no detection of the virus in California cattle and that a network of public and private veterinarians was in close communication with the dairy industry and individual farmers.
Despite these assurances, however, some experts have questioned the speed of the government’s response to the outbreak.
Eric Topol, a professor of molecular medicine at Scripps Research, said that while he was glad the government was finally coming together in a united front to present information Wednesday, “it certainly took a while.”
He said the government probably knew for weeks – or even months – about the positive samples. He noted the publication Sunday evening of 239 DNA sequences which revealed the presence of the virus in samples of commercial milk.
“They didn’t get this footage overnight,” Topol said. “They got them.”
Analysis of these sequences suggests a single origin of the virus in dairy cattle at some point in late 2023 or early 2024 – most likely from an infected bird, but possibly from infected feed.
“I don’t know if we’re out of the woods, because now there’s so much spread among livestock in the country that all we need is one bad recombination event,” Topol said, referring to the possibility of the genes from a human flu virus mixing with those from the bovine virus to create a new or modified version that could be more problematic for humans.
“It’s like Covid is all over again,” Topol said, recalling the authorities’ response in the weeks and months after the pandemic began to spread in early 2020.
At Wednesday’s news conference, officials said researchers are actively testing virus particles found in milk samples in the lab to see if they can be grown either in cell cultures or in 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.
Government officials and researchers said they were expanding their monitoring and monitoring and suggested more information would be released in the coming days.
They also issued a federal order requiring laboratories to report any dairy cattle testing positive for avian influenza or any type of influenza A, as well as testing all lactating dairy cattle moving interstate. Additionally, any farm where bird flu-positive cows have been found will have to undergo an epidemiological investigation and movement tracking, said Mike Watson, administrator of the Animal and Plant Health Inspection Service.
Details about how many milk samples were tested, as well as where, how and why they were obtained, were not shared with reporters.
At least one outside expert said he doubted government researchers could find an active virus in milk samples.
“I would bet five mortgage payments” that they won’t find live or active virus in the samples, said Michael Payne, a researcher and outreach coordinator at UC Davis’ Western Institute for Food Safety and Security.
“As an Eagle Scout (Northeast Georgia Council, 1976), I tell you this with complete honesty and transparency: I would not hesitate to drink, nor would I hesitate to serve my family, pasteurized milk from any U.S. dairy herd. States,” he said.
At the news conference, officials said they were also closely monitoring cases of human infection.
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 is actively monitoring 44 people “who are considered exposed and at risk of infection.”
So far, only one human case has been identified in the current outbreak, and that person is believed to have only mild symptoms.
However, in other places where humans have been infected, the virus has made people sicker and has even been fatal. According to the World Health Organization, which tracks the evolution of the virus, between January 2003 and February 2024, 887 confirmed cases of human infection were recorded in 23 countries. Of these, 462 were fatal.
Although the current virus has not evolved the ability to become more transmissible to humans, researchers have noted some worrying mutations.
These include observations of spread of the virus between cows within the same herd, from cows to poultry, and movements of the virus between dairies associated with movements of cattle. It has also been detected in cows that showed no clinical signs of the disease, suggesting that it goes unnoticed.
Additionally, on April 16, a USDA microbiologist “identified a change” in a sample from McAllen, Kan., that appeared to show a mutation that would make it more transmissible between mammals, said Watson, who is responsible for the USDA. He said further analysis from the CDC showed “an overall low risk.”
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