“Milk is safe.” That was the takeaway from H5N1 research reported this week in the Journal of Virology, which tested nearly 300 milk products from 132 processors to better understand the spread of the disease.
The milk processing pipeline includes multiple layers of protection, said Erica Spackman, a virologist at the U.S. Department of Agriculture. Microbiological surveillance of milk products can identify pathogens, and milk from cows with mastitis or other disease conditions does not enter the food supply. Finally, heating during the pasteurization process can destroy highly pathogenic avian flu and other, more common bacterial pathogens.
“Just like bacterial pathogens that occur in milk, or other viruses that could occur in milk, the sanitation processes that are in place are getting rid of the pathogens,” she said.
In March 2024, dairy cows in Texas were found to be infected with H5N1 bird flu — the first known case of the virus spreading to cattle. Since then, H5N1 has been found in about 200 animals (and 3 people) across 12 states, according to the Centers for Disease Control and Prevention.
The virus was soon detected in raw milk, leading researchers to investigate whether dairy products pose a risk to consumers.
Bird flu primarily infects and spreads among migratory birds and can be transmitted to domestic poultry, but the virus has been detected in cats, dogs and juvenile goats, as well as a polar bear in Alaska and elephant and fur seals in the Antarctic. However, the discovery of H5N1 on dairy farms in March was a surprise.
Soon after the discovery, diagnostic testing revealed that an infectious form of the virus was present in raw milk, suggesting the virus passes from cow to milk. That finding led the U.S. Food and Drug Administration and the USDA to investigate whether pasteurization effectively eliminated risks posed to consumers. Between April 18 and April 22, 2024, researchers used real-time PCR to analyze 297 samples of pasteurized retail milk products, including 23 types of products, collected from 17 states.
“We did a viability assay to detect live virus and went as sensitive as we could to get even the least little bit of virus, but couldn’t detect anything,” Spackman said. Using real-time PCR, the researchers did identify viral genetic material in 20 percent of samples.
“It looks like the virus is just totally inactivated,” she said.
Spackman said the new findings “give us reassurance that what we have been doing — pasteurization — is keeping us safe from what we don’t know about.”
The research also comes just a day after an Annenberg Public Policy Center survey that noted that much of the public fails to appreciate risk of consuming raw milk. It stated that nearly a quarter of Americans either think incorrectly that pasteurization is not effective at killing bacteria and viruses in milk products (4 percent) or are not sure whether this is true (20 percent).
The Journal of Virology is part of the American Society for Microbiology, one of the largest professional societies dedicated to the life sciences and is composed of 32,000 scientists and health practitioners. ASM’s mission is to promote and advance the microbial sciences.
