In the labyrinthine corridors of public health, few threats loom as insidiously as the prospect of foodborne diseases. Recently, a study from Cornell University, funded by the US Food and Drug Administration (FDA), has cast a shadow over the safety of raw cheese, revealing a hidden danger that has long been underestimated. This revelation has sparked a renewed urgency in the debate surrounding raw dairy products and their potential to harbor infectious viruses, particularly in the context of the ongoing bird flu outbreak.

Raw milk cheeses, those crafted from milk that has not undergone the sanitizing process of pasteurization, have long been a subject of fascination and concern. These cheeses, with their rich, unadulterated flavors, are beloved by connoisseurs but carry with them an inherent risk. Since 1949, federal law has permitted the sale of raw milk cheese nationwide, provided it is aged for at least 60 days. This regulation was established on the premise that the aging process allows natural acids and enzymes to develop, which were believed to neutralize harmful pathogens. However, the recent study from Cornell University has shattered this long-held assumption, exposing a vulnerability in our food safety protocols.

The study, led by Dr. Diego Diel, an associate professor of virology at Cornell, has uncovered a startling fact: the H5N1 bird flu virus can survive in raw cheese for months, rendering the 60-day aging requirement insufficient to eliminate the risk of infection. This finding is particularly alarming given the current bird flu outbreak, which continues to infect not only poultry but also dairy cattle and an increasing number of other animal species. The study builds on previous research by the same team, which demonstrated that the H5N1 virus could remain infectious in refrigerated raw milk for up to eight weeks. The stability of the virus in these dairy products is attributed to the complex molecular matrix of milk and cheese, which provides a protective environment for the virus, allowing it to thrive even at refrigeration temperatures.

The implications of this study are profound, challenging the prevailing wisdom that food does not pose a significant risk for bird flu transmission. Robert F. Kennedy Jr., the Secretary of the US Department of Health and Human Services, has publicly stated that bird flu cannot be contracted through food, asserting that eggs, milk, and meat from infected animals are safe to consume. However, this assertion is only partially accurate. There have been documented cases of cats and other animals becoming infected through raw cow's milk and raw pet food. Moreover, at least three confirmed human infections have occurred where the source of exposure to the H5N1 virus could not be definitively identified. While there have been no confirmed reports of illness resulting from the consumption of bird flu-contaminated foods, including raw milk cheese, the study raises legitimate concerns about the potential for such transmission.

Dr. Diel acknowledges that his study was not specifically designed to determine whether humans can be infected by consuming contaminated food. Nevertheless, he asserts that the risk of infection is real and depends on several factors, including the dose of the contaminated product ingested and the specific strain of the virus present. The study focused on the B3.13 strain of the virus, which emerged in the US in March 2024 and has been associated with mild disease in humans. However, a more virulent strain, D1.1, which has caused severe illness in some human cases, has also been detected in cattle, further escalating the potential risk.

To test the stability of the H5N1 virus in cheese, the researchers created mini cheeses using milk spiked with the virus. They varied the pH levels of the cheeses to determine whether acidity played a role in virus survival. The cheeses were produced at three pH levels: 6.6, 5.8, and the most acidic formulation at 5.0. Over the course of the study, the researchers monitored the infectiousness of the virus in the cheeses, using the gold standard test of injecting samples into fertilized chicken eggs. The results were both surprising and concerning. While the virus levels dropped slightly in cheeses with pH levels of 6.6 and 5.8 after the first seven days, the virus remained infectious throughout the entire two-month aging period. Notably, no live virus was detected in the cheese with the lowest pH of 5.0, suggesting that increased acidity may inactivate the virus and render the cheese safer for consumption.

These laboratory findings were corroborated by real-world examples. The researchers tested raw milk cheese samples from a farm that had inadvertently used milk from cows infected with bird flu. The results mirrored those of the laboratory study, with virus levels remaining high and infectious throughout the two-month aging process. The authors of the study concluded that the highly pathogenic avian influenza (HPAI) H5N1 virus exhibits remarkable stability throughout the cheese-making process, posing a significant risk to public health.

The study's findings have not gone unnoticed by experts in the field. Dr. Seema Lakdawala, an associate professor of microbiology and immunology at Emory University, who has been studying the transmission of H5N1, noted that the study's results are consistent with previous observations on the virus's stability in milk. She explained that milk's unique composition can alter the pH required to inactivate the virus, making it more resilient on surfaces and necessitating a lower pH for neutralization. This insight underscores the importance of understanding the complex interplay between dairy products and viral pathogens.

The FDA, recognizing the gravity of these findings, has taken steps to address the potential threat. In addition to posting the Cornell study's results, the FDA has conducted its own sampling study of raw cheese, testing 110 samples from store shelves across the country. Preliminary results indicate that 96 of these samples were negative for the H5N1 virus, suggesting that the cheeses were likely not made from contaminated milk. However, the results for 14 samples are still pending, highlighting the ongoing need for vigilance.

The FDA's efforts extend beyond raw cheese, with a broader sampling of 464 pasteurized dairy products, including milk, cheese, butter, and ice cream. All of these samples tested negative for viable H5N1, reinforcing the effectiveness of pasteurization in neutralizing the virus. Multiple research studies have confirmed that common pasteurization methods are sufficient to inactivate the H5N1 virus, providing a crucial safeguard against foodborne transmission.

Despite these reassuring findings, experts emphasize that the study serves as a stark reminder of the importance of surveillance and the need to avoid consuming raw milk products. Dr. Lakdawala stresses that ensuring the absence of bird flu in milk products and promoting the consumption of pasteurized dairy products is paramount. The study's revelations have reignited the debate over the safety of raw dairy products, highlighting the delicate balance between preserving traditional food practices and protecting public health.

In conclusion, the Cornell University study has unveiled a hidden peril lurking within raw cheese, challenging long-standing assumptions about food safety and the effectiveness of aging as a protective measure. The remarkable stability of the H5N1 virus in raw cheese underscores the need for continued research, heightened surveillance, and a renewed commitment to pasteurization. As the bird flu outbreak continues to evolve, the findings of this study serve as a clarion call to policymakers, public health officials, and consumers alike. The safety of our food supply must remain a paramount concern, and the lessons learned from this study must inform our efforts to safeguard public health in the face of emerging threats.