Bird flu virus survives in raw-milk cheese for months

Recent research published in Nature Medicine has found that the H5N1 bird flu virus can remain infectious in raw-milk cheese for as long as 120 days. Conducted by researchers at Cornell University, the study demonstrated that the virus’s stability is influenced by specific pH levels in the cheese production process. The research indicates potential public health risks associated with consuming unpasteurized dairy products tainted with the virus.

The highly pathogenic avian influenza H5N1 predominantly affects wild birds but has also appeared in poultry and dairy cows in the U.S., with human cases reported among livestock workers. The study highlights the presence of the virus in the milk of infected cows and suggests that various pasteurization methods effectively inactivate it, though raw products still pose a risk.

In testing, the virus proved stable during cheese production and could last up to 120 days under most pH conditions, except at a pH of 5.0, which successfully inactivated the virus. Despite experiments showing ferrets ingesting contaminated milk became infected, those consuming contaminated cheese did not, indicating the need for further research.

This research points to a need for updated food safety regulations, especially considering the current U.S. requirement for a 60-day monitoring period for raw-milk cheese, which may be inadequate for ensuring safety from the H5N1 virus. The study authors recommend examining other raw dairy products for similar risks.

• Why it matters: The findings could lead to changes in food safety regulations regarding raw dairy products, emphasizing the importance of pasteurization and enhanced monitoring.
• The latest: Researchers have reported that heat treatment of raw milk at temperatures above 54°C effectively inactivates the H5N1 virus within 15 minutes.