On Mar. 14, 2025, researchers from Cornell University reported results from a study that show the Aging Process alone may not be effective in eliminating viable H5N1 in raw milk cheese.

After the first detection of HPAI H5N1 in dairy cattle in March 2024, the U.S. Food and Drug Administration (FDA) engaged in research and other efforts with industry, federal, and state partners to ensure the continued effectiveness of the federal-state milk safety system.

Aging is a minimum process specific raw milk cheeses must undergo to meet standard of identity regulations before entering interstate commerce. While the research did not represent all commercial processes for producing raw milk cheese, results being previewed in a pre-print suggest that aging raw milk cheese for 60 days or longer is not effective at eliminating viable H5N1 in the cheese.

H5N1 survived (i.e., was viable) in non-heat-treated raw milk cheese through and beyond the 60-day aging process. However, heating raw milk at 54°C (130°F) for at least 15 minutes or 60°C (140°F) for at least 10 seconds inactivated H5N1 in this research. 

The FDA is confident that pasteurization is effective at inactivating H5N1, and that the commercial, pasteurized milk supply is safe. To date, FDA testing of pasteurized dairy products and aged raw milk cheese intended for retail has not detected infectious H5N1.