March 14, 2025

Interim Results from FDA 60-day Aged Raw Milk Cheese Research Don’t Detect H5N1 in Samples Collected to Date

Beginning in December 2024, the FDA initiated an assignment sampling 60-day aged raw milk cheese. The first sample was taken January 2, 2025, and sample collections are anticipated to be complete by the end of March 2025. As of March 10, 2025, 110 samples of the planned 299 have been collected. Of those 110 samples, 96 were negative by PCR (meaning that H5N1 was not detected in the analyzed samples), and 14 are still in progress. Final results are expected later this spring.

Research Results from Cornell University Suggest that the Aging Process Alone May Not Be Effective in Eliminating Viable H5N1 in Raw Milk Cheese

The FDA is continuing to work with Federal and state partners to address the ongoing outbreak of HPAI A (H5N1) in dairy cattle. The FDA has sampled a total of 464 pasteurized dairy products, including milk, cheese, butter, and ice cream, all were negative for viable H5N1. In addition, multiple research studies have confirmed that pasteurization inactivates the virus.

FDA and New York State funded research conducted at Cornell University to assess whether aging raw milk cheese for at least 60 days is effective in reducing or eliminating viable H5N1.

Research on Aged Raw Milk Cheese

To better understand whether aging raw milk cheese is effective at reducing or eliminating viable H5N1, the FDA funded specific research at Cornell University. 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-printExternal Link Disclaimer 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.

Information for Consumers

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.
Consumers who want to know if their cheese has been made with raw milk may check the product label. While there is no express Federal requirement for the labeling of cheeses to disclose on the ingredient list whether the milk used in manufacture was raw or pasteurized, many cheeses do disclose on the ingredient list (or elsewhere on the product label) if the milk used is pasteurized or raw. The FDA is not aware of any H5N1 illnesses to date from the consumption of aged raw milk cheese products. The FDA is continuously monitoring the HPAI situation and working together with USDA, CDC, state partners, academia, and industry on ways to mitigate the impact of this ongoing outbreak using a One Health approach to understand and reduce H5N1.

Information for Industry

The FDA continues to recommend that dairy producers monitor herds for H5N1 infection by enrolling in USDA or state testing programs. If a herd becomes infected with H5N1, the USDA recommends that dairy producers segregate clinically ill cows from the rest of the milking herd. The FDA recommends dairy processors not use milk from infected cows in the production of raw milk products, such as raw milk cheese, and reminds manufacturers that heat treating or pasteurization are both effective measures that inactivate H5N1. Research to date has demonstrated heating raw milk at 54°C (130°F) for at least 15 minutes or 60°C (140°F) for at least 10 seconds inactivates H5N1 in raw milk. Additionally, the researchers determined that manufacturing non-heat-treated raw milk cheese at a pH of 6.6 or 5.8 did not inactivate H5N1, whereas a pH of 5.0 led to rapid inactivation of H5N1. Additional research is needed to determine if pH adjustment is a practical intervention.