Cornell University Study Finds H5N1 Virus Can Persist in Raw Milk Cheese Months

New research from Cornell University has cast a shadow over the long-held assumption that the 60-day aging process for raw milk cheese reliably neutralizes harmful pathogens. In a startling revelation, scientists found that the H5N1 avian influenza virus, a pathogen of global concern, can persist in raw cheese for months, particularly in varieties with lower acidity. This discovery raises questions about the safety of raw milk cheeses, even those subjected to the aging process mandated by U.S. regulations. While the findings are preliminary and await peer review, they underscore the need for a closer look at how food safety practices intersect with emerging infectious diseases.

Rethinking the Safety of Raw Milk Cheese in the Context of H5N1

The study, funded by the U.S. Food and Drug Administration (FDA), tested 110 raw cheese samples for traces of the H5N1 virus. Encouragingly, 96 samples showed no signs of active or inactive virus, suggesting that most were likely made from uncontaminated milk. However, the remaining findings were less reassuring. In cheeses with lower acidity levels, the virus remained infectious throughout the aging process, defying the widely held belief that the 60-day aging rule is a reliable safeguard. By contrast, cheeses with a pH level of 5.0 or lower—indicating higher acidity—effectively inactivated the virus, as did pasteurization.

The implications of these findings are significant, particularly for raw milk cheese producers and consumers who prize these artisanal products for their unique flavors and textures. While no cases of H5N1 infection from consuming raw milk cheese have been documented, the study notes that dairy workers have contracted the virus through contact with raw milk. This raises the specter of potential risks in the production chain, even if the end product has not yet been linked to human illness.

The H5N1 virus, often referred to as bird flu, has already proven its capacity to jump from animals to humans, albeit in rare instances. While the virus primarily affects poultry, sporadic human infections have been documented, usually in individuals who had close contact with infected birds or their secretions. The virus’s ability to survive in raw cheese for extended periods adds a new layer of complexity to the ongoing efforts to contain its spread.

The FDA has been quick to reassure the public, emphasizing that pasteurized dairy products remain safe for consumption and that no cases of H5N1 illness have been linked to aged raw milk cheese. Nevertheless, the agency acknowledges the need for further research to confirm these preliminary findings and to determine whether additional safety measures might be warranted.

For raw milk cheese enthusiasts, this news may feel like a wake-up call. The artisanal cheese movement has long celebrated raw milk as a cornerstone of authenticity and flavor, often arguing that pasteurization diminishes the complexity of the final product. Yet, the risks associated with raw milk cheeses have always been a point of contention. Advocates often point to the meticulous care taken by small-scale producers, while critics highlight the potential for contamination by pathogens like Listeria, Salmonella, and now, H5N1.

The study’s findings are particularly relevant in the context of a global food system increasingly shaped by zoonotic diseases—those that can jump from animals to humans. From the COVID-19 pandemic to recurring outbreaks of bird flu, the interconnectedness of human, animal, and environmental health has never been more apparent. The persistence of H5N1 in raw cheese serves as a reminder that food safety is not a static field but one that must continuously adapt to emerging threats.

For policymakers, the challenge lies in balancing public health concerns with the interests of small-scale producers and consumers. Stricter regulations could impose significant burdens on artisanal cheesemakers, many of whom already operate on razor-thin margins. On the other hand, failing to address the risks could undermine public confidence in the safety of raw milk products, with potentially far-reaching consequences for the industry.

The study also raises broader questions about the role of science in shaping food safety practices. The 60-day aging rule, long considered a gold standard, now appears less robust than previously thought. This underscores the importance of revisiting established guidelines in light of new evidence, even when doing so may be inconvenient or controversial.

As the findings await peer review, it’s worth reflecting on the broader implications for consumers. For those who prioritize safety above all else, pasteurized products offer a clear and reliable choice. For others, the allure of raw milk cheese may still outweigh the risks, particularly given the absence of confirmed cases linked to its consumption. Ultimately, the decision may come down to a matter of personal preference and risk tolerance.

In the meantime, the study serves as a timely reminder of the intricate interplay between food production, public health, and scientific discovery. As researchers continue to probe the mysteries of H5N1 and its survival in unexpected environments, one thing is clear: the quest for safer, more resilient food systems is far from over. Whether through advances in technology, changes in regulation, or shifts in consumer behavior, the path forward will require a collective effort to navigate the challenges—and opportunities—of an increasingly complex world.