Pasteurization fully inactivates the H5N1 chook flu virus in milk — even when viral proteins linger.
Ingesting correctly pasteurized milk contaminated with avian influenza remnants gained’t enhance vulnerability to the an infection, researchers report in September 26 in Science Advances. Warmth therapy fully neutralized the extremely pathogenic avian influenza H5N1 virus whereas leaving some viral genomic materials intact. These remnants didn’t make mice sick after they repeatedly drank the milk. However consuming the fragments didn’t enhance mice’s immune methods in opposition to later an infection both.
“Pasteurized milk containing H5N1 is protected; uncooked milk isn’t,” says Stacey Schultz-Cherry, a virologist at St. Jude Kids’s Analysis Hospital in Memphis, Tenn.
Because the first confirmed an infection in the USA in dairy cows in 2024, H5N1 has unfold to 17 states. That features Nebraska for the primary time, the U.S. Division of Agriculture reported September 15. The unfold is regarding as a result of the virus can spill over to people.
The U.S. Facilities for Illness Management and Prevention has confirmed a number of H5N1 infections in individuals, together with one loss of life. CDC has linked these circumstances to wild birds, yard flocks and unpasteurized or uncooked milk.
U.S. meals and security regulators have stated that milk pasteurized at 72° Celsius for 15 seconds is protected for human consumption. However laboratory assessments have picked up fragments of viral genomic materials in it, together with RNA and the protein hemagglutinin, the “H” within the identify, that helps H5N1 latch onto cells.
“Detecting viral RNA is like seeing a footprint or a shadow. It reveals one thing was there, however it’s not alive or able to shifting by itself,” Schultz-Cherry says.
Though the presence of those fragments doesn’t pose a illness threat when consumed, the impact of the viral remnants in pasteurized milk has been unclear. May they suppress the immune system and make a later an infection worse? May they bolster the immune system to combat a future an infection? Or do they do nothing?
To search out out, Schultz-Cherry and colleagues obtained uncooked cow’s milk that was freed from the H5N1 virus. The crew then added a excessive degree of H5N1 to re-create a worst-case contamination state of affairs earlier than pasteurizing the milk underneath normal dairy circumstances: 72° C for 15 to 30 seconds. Pasteurization persistently inactivated the virus, assessments confirmed.
Mice have been then fed the pasteurized milk orally for 5 days and monitored for a complete of 21 days from the beginning of the experiment. After 21 days, the mice have been uncovered to a deadly dose of dwell virus.
Mice fed the pasteurized milk with inactivated H5N1 and people fed pasteurized milk that had by no means contained the virus died at the same fee. That reveals that repeated publicity to inactivated viral remnants within the milk didn’t immediate any immune response that may arm the mice to combat a brand new an infection or suppress the immune system, making a later an infection worse.
Whereas it’s reassuring to know that pasteurization works, we must always actually attempt to maintain H5N1 out of the milk provide fully, says Andrew Pekosz, an immunologist at Johns Hopkins Bloomberg College of Public Well being. Not all noncommercial or dwelling pasteurization might meet strict requirements, and CDC knowledge recommend uncooked milk might be a supply of H5N1 spillover to people.
