Bird Flu in Cheese: Scientists Find H5N1 Survives in Raw Milk Products

Researchers have discovered that the H5N1 bird flu virus can survive in raw milk cheese, raising new food safety concerns. The study found that the virus remained infectious even after 120 days of aging, twice as long as current FDA safety standards require. However, cheeses with high acidity, such as feta, showed no trace of the virus, suggesting that acidity offers strong protection against contamination.

How the Virus Survives

The research team at Cornell University studied how the H5N1 virus behaves in different types of raw milk cheese. They found that when cheese had a pH between 5.8 and 6.6, the virus stayed alive. In contrast, cheeses with a pH of 5 or lower showed no infection. This highlights how acidity plays a crucial role in preventing viral survival. The virus’s ability to persist despite long aging periods suggests that current safety regulations may not be enough.
Animal tests provided more insight. Ferrets that drank contaminated raw milk became infected, while those that ate the same milk made into cheese did not. Scientists believe the virus in milk may have more direct contact with throat tissues, while cheese limits that exposure.

Preventing Future Contamination

Experts say cheesemakers can reduce risks by testing milk for viruses before production. Another method is gently heating milk to sub-pasteurization levels, which kills the virus but keeps traditional raw milk flavor. Researchers also tested commercial cheddar samples from the FDA and found traces of H5N1 in all of them. These findings stress the need for stricter monitoring and testing of unpasteurized dairy products.
The study, published in Nature Medicine, was supported by the FDA and New York State Department of Agriculture and Markets. It provides crucial guidance for the dairy industry to protect consumers from emerging viral threats like bird flu in cheese.