Study Reveals H5N1 Virus Stability in Raw Milk Cheese

In a recent study published in Nature Medicine, scientists unveiled important findings regarding the stability of the highly contagious H5N1 avian influenza virus in cheese products made from raw milk. This study opens new horizons for understanding how the virus interacts with dairy products and its impact on food safety.

Virus Stability in Raw Cheese

The study focused on exploring the ability of the H5N1 virus to persist in raw cheese. Dr. Diego Dell, a professor of virology, explained that the motivation behind this research was previous discoveries showing high levels of virus secretion in milk from infected cows, and the virus’s success in remaining viable in refrigerated raw milk for extended periods.

Under the guidelines of the U.S. Food and Drug Administration, cheese made from raw milk must be aged for at least 60 days at a temperature of 35 degrees Fahrenheit or higher. However, researchers found that the virus remained infectious even after 120 days of aging at 39 degrees Fahrenheit, suggesting that the standard aging period may not be sufficient to eliminate viral contamination.

The Role of Acidity in Cheese Safety

Acidity plays a vital role in the safety of cheese products. Acidity levels below 7 are considered acidic, and most cheeses have a pH ranging from 5.4, as in cheddar cheese, to 7, as in camembert cheese. Some types, like feta, can drop to 4.6 or lower.

The results showed that the virus remained viable in cheese with a pH level between 5.8 and 6.6, while no virus was detected in cheeses with a pH of 5 or lower. These findings highlight the importance of acidity as a key factor in deactivating the virus during cheese production.

Reducing Contamination Risks

Dr. Dell pointed out that steps can be taken to reduce contamination risks, such as testing milk before cheese production and using virus-free milk. Additionally, heating milk to temperatures below pasteurization can inactivate the virus while preserving the raw cheese characteristics valued by artisanal producers.

Nicole Martin, a co-author of the study and assistant research professor in dairy food microbiology, emphasized the importance of this work in providing data-driven knowledge and practical recommendations for the dairy industry in facing this outbreak.

Animal Testing and Understanding Transmission

The study also included animal testing using rodents, which are highly susceptible to the H5N1 virus. These animals were fed raw milk and raw cheese contaminated from the study. The results showed that some rodents that drank raw milk became infected, while those that consumed raw cheese did not.

Dell suggested that this difference might be due to how the virus interacts with the body. The liquid milk may allow greater contact of the virus with the mucous membranes in the throat, while cheese reduces the exposure time needed for the virus to initiate infection.

Conclusion

This study highlights the challenges facing the dairy industry in the presence of the H5N1 virus and presents possible solutions to mitigate its risks. Understanding how the virus stabilizes in raw cheese products and the role of acidity in deactivating it offers an opportunity to improve food safety standards and ensure consumer health.