Raw milk cheese has been a popular favorite among foodies and artisanal cheese enthusiasts for centuries. With the recent news on the transmission of H5N1 avian influenza (bird flu) among American dairy cows, however, questions are being raised: Is raw milk cheese safe to consume? Let’s take a look at what new studies have to say—and what it implies for your next visit to the cheese counter.
Why Raw Milk Cheese Is Back in the Spotlight
Historically, bird flu has been linked to poultry. But the situation changed when a strain of H5N1 was discovered in dairy cows in multiple states, and occasionally, it infected people. This new turn of events led the FDA, CDC, and scientists at Cornell University to investigate dairy products, particularly those from raw (raw, unpasteurized) milk.
What the Science Says
In the United States, raw milk cheese is legally required to be aged for a minimum of 60 days before it can be sold. It was thought that this period would kill off harmful bacteria. But a new Cornell University study, paid for by the FDA and the state of New York, disputes that notion—at least where viruses are concerned.
Scientists made cheese from raw milk that was either deliberately contaminated with the H5N1 virus or from cows infected during an outbreak. They then tracked how long the virus persisted through the cheese-aging process. The findings were astonishing:
- At typical pH levels of cheese (5.8 and 6.6), H5N1 survived for 60 days or more.
- Only at an extremely acidic pH of 5.0 did the virus quickly perish.
- The virus also lasted almost two months in cold raw milk.
Why Aging Isn’t Enough for Viruses
The 60-day aging regulation is good for keeping out bacteria such as Listeria and Salmonella. But viruses are different. The fat and protein of cheese, plus cool aging temperatures, might even extend the life of the virus, says study co-author Nicole Martin, PhD.
Keith Poulsen, DVM, PhD, of the University of Wisconsin-Madison, makes clear that although the 60-day rule has an excellent record of protecting against bacterial illness, it is not necessarily sufficient to guard against H5N1—particularly if the cheese is processed on a farm where there are infected cows.
Pasteurization and pH: What Keeps Cheese Safe
There is good news: pasteurization is still effective. Heating milk to specific temperatures for certain lengths of time successfully destroys H5N1:
- 54°C (130°F) for 15 minutes
- 60°C (140°F) for 10 seconds
To be sure, in testing hundreds of pasteurized dairy products, the FDA detected no trace of the virus. So, pasteurized milk, cheese, butter, and ice cream are still safe bets.
Acidity (pH) plays a part as well. The Cornell study showed that a pH of 5.0 killed the virus quickly, but most raw milk cheeses aren’t that acidic when produced under usual conditions.
What It Means to Cheese Enthusiasts
To date, there are no reported instances of transmission of bird flu through raw milk cheese. Small, artisanal U.S. manufacturers are primarily the producers of raw milk cheese. They employ milk from well-managed herds, limiting the chances of infection.
Nevertheless, if you are worried, follow these few prudent precautions:
- Read labels for “unpasteurized” or “raw milk.” If you are unsure, inquire from the producer or retailer.
- Choose pasteurized-milk cheeses if you prefer to err on the side of caution, particularly in the midst of active outbreaks.
- Keep abreast of health officials’ recommendations as new information becomes available.
It’s also important to realize that the FDA does not yet mandate labeling cheese packaging as being made from raw or pasteurized milk, so a bit of added vigilance might be required if you wish to steer clear of raw milk products.
Experts Are Watching Closely
The FDA, CDC, and USDA are collaborating closely with researchers and local governments to monitor dairy supply safety. They recommend that dairy farmers test herds for H5N1 and not use milk from infected cows in raw milk products.
David J. Topham, PhD, of the University of Rochester, points out that H5N1 isn’t particularly hardy in cheese to begin with—it simply hasn’t been researched extensively until now because viral transmission via cheese used to be uncommon.
Stay Informed, Choose What Feels Right
At the moment, the risk to consumers is low. But the science continues to change, and new research is informing a better idea of how to best ensure public health. If raw milk cheese is something you enjoy, this isn’t necessarily a reason to avoid it, but it is a good moment to be educated and make decisions that feel good for you. Your cheese plate doesn’t have to be off-limits—just make sure what’s on it aligns with your comfort level and the latest safety recommendations.