Commonground
Senior Moderator
September 26, 2025
Scientists at St. Jude Children’s Research Hospital found that viral components in pasteurized milk did not alter flu immunity or increase susceptibility to infection.
Proteins and genetic material from H5N1 influenza viruses have been found in pasteurized milk in the United States, but a study from St. Jude Children’s Research Hospital shows those inactive viral pieces represent little to no health risk. As the H5N1 outbreak in dairy cows continues in the U.S., commercial milk remains contaminated by viral pieces. However, the pasteurization process kills the virus. The researchers tested whether the resulting noninfectious viral materials could teach the immune system that these viral components were harmless, thus increasing susceptibility to influenza infections. They found that H5N1-contaminated milk that was pasteurized did not significantly affect the immune system in laboratory models. Unpasteurized milk remains a health concern. The findings were published today in Science Advances.
“We found that consuming pasteurized milk multiple times, even if it has inactivated H5N1 virus, poses minimal health risks,” said corresponding author Stacey Schultz-Cherry, PhD, St. Jude Department of Host-Microbe Interactions. “We observed no benefit or detriment to subsequent influenza infection.”
The scientists were originally concerned that regularly drinking inactivated viral components in milk may teach the immune system that these molecules were safe. This loss of immunity against materials in food is called oral tolerance, which prevents humans from developing unwanted immune reactions against what they consume. However, if people gained oral tolerance to flu’s viral proteins, it could lead to greater susceptibility to later influenza infections if the body no longer recognizes the viral components as part of an invader.
To learn if drinking contaminated pasteurized milk created oral tolerance of influenza viruses, the researchers took uncontaminated milk or milk contaminated with H5N1, which were both then pasteurized, and gave them to mice. The mice were given the milk over five days, mimicking how a person would consume it over time. Weeks later, the scientists challenged the mice with an H5N1 infection. There was no difference in how the infection proceeded between the two groups.
“We found an influenza infection after repeated exposure to H5N1 virus in pasteurized milk was normal, with no adverse events,” said first author Pamela Brigleb, PhD, St. Jude Department of Host-Microbe Interactions. “We saw no evidence of it worsening the disease.”
https://www.stjude.org/media-resour...teurized-milk-poses-minimal-health-risks.html
Scientists at St. Jude Children’s Research Hospital found that viral components in pasteurized milk did not alter flu immunity or increase susceptibility to infection.
Proteins and genetic material from H5N1 influenza viruses have been found in pasteurized milk in the United States, but a study from St. Jude Children’s Research Hospital shows those inactive viral pieces represent little to no health risk. As the H5N1 outbreak in dairy cows continues in the U.S., commercial milk remains contaminated by viral pieces. However, the pasteurization process kills the virus. The researchers tested whether the resulting noninfectious viral materials could teach the immune system that these viral components were harmless, thus increasing susceptibility to influenza infections. They found that H5N1-contaminated milk that was pasteurized did not significantly affect the immune system in laboratory models. Unpasteurized milk remains a health concern. The findings were published today in Science Advances.
“We found that consuming pasteurized milk multiple times, even if it has inactivated H5N1 virus, poses minimal health risks,” said corresponding author Stacey Schultz-Cherry, PhD, St. Jude Department of Host-Microbe Interactions. “We observed no benefit or detriment to subsequent influenza infection.”
The scientists were originally concerned that regularly drinking inactivated viral components in milk may teach the immune system that these molecules were safe. This loss of immunity against materials in food is called oral tolerance, which prevents humans from developing unwanted immune reactions against what they consume. However, if people gained oral tolerance to flu’s viral proteins, it could lead to greater susceptibility to later influenza infections if the body no longer recognizes the viral components as part of an invader.
To learn if drinking contaminated pasteurized milk created oral tolerance of influenza viruses, the researchers took uncontaminated milk or milk contaminated with H5N1, which were both then pasteurized, and gave them to mice. The mice were given the milk over five days, mimicking how a person would consume it over time. Weeks later, the scientists challenged the mice with an H5N1 infection. There was no difference in how the infection proceeded between the two groups.
“We found an influenza infection after repeated exposure to H5N1 virus in pasteurized milk was normal, with no adverse events,” said first author Pamela Brigleb, PhD, St. Jude Department of Host-Microbe Interactions. “We saw no evidence of it worsening the disease.”
https://www.stjude.org/media-resour...teurized-milk-poses-minimal-health-risks.html