Protecting families from contaminated food and water
All fields are required
Protecting families from contaminated food and water
Posted in Food Safety,Our Blog,Raw Milk on October 22, 2025
A recent Cornell University study found that bird flu in cheese can survive for six months! With the recent revival of increased consumption of raw milk and raw milk cheeses in the United States, this is a huge finding.
How does bird flu get into raw milk and raw milk cheese? What study discovered this finding? How do you know if you have bird flu?
Here’s what we know so far about bird flu in cheese.
A survey taking place between 2016 and 2019 by the U.S. Food and Drug Administration (FDA) found that 4.4% of US adults reported consuming raw milk at least once a year. They also found that 1.6% reported consuming it frequently, and another 1.6% reported consuming raw milk cheeses.
The Make Food Safe Blog recently reported the surprising new poll of public perception when it comes to raw milk. The Annenberg Public Policy Center (APPC), of the University of Pennsylvania conducted a poll. The survey indicated that while the majority (56%) of U.S. adults believed that raw milk (from cows, goats, or sheep) are less safe. The margin was not all that wide. For 44% did not believe it is less safe.
In fact, 12% indicated that raw milk is “just as safe to drink” and 6% believe that it is “safer to drink” than other milk options.
When the question was posed in a different way, asking if they believed that raw milk included an increased risk of foodborne illness, nearly a third indicated that there was a risk. However, the survey found that 14% indicated that raw milk has no effect on risk of foodborne illness. Most people (51%) were not sure.
With more and more consumers, well, consuming raw milk and cheese made from it, bird flu in cheese is a serious consideration.
But first, how does bird flu get into raw milk?
It seems like a strange concept. You assume that bird flu should affect birds. Which it does. Hence the name. HPAI (highly pathogenic avian influenza) H5N1.
Fortunately, the “highly pathogenic” aspect only applies to birds.
For now.
Though recent events have proven that the virus has evolved to attack not only our feathered friends. But cows, cats, mice, and even humans.
Bird flu gets into raw milk when a lactating cow becomes infected with bird flu. Often from wild birds in the cow’s environment. The virus is shed from the mammary glands into the milk from an infected cow.
Bird Flu Virus is Excreted into the Milk from an Infected Lactating Cow
Certain mutations have allowed the virus to infect these bovine beauties, presenting a dilemma for the dairy industry. For cows do not show the same symptoms as chickens, turkey’s or other poultry (usually rapid respiratory distress followed by death).
In fact, most cows are asymptomatic!
The only signal given to the rancher is reduced milk production. Only routine surveillance testing and close monitoring of milk output indicates the presence of bird flu in dairy herds.
Most of the cow’s milk consumed in the United States is pasteurized, and therefore safe for consumption. The heat treatment process of pasteurization has been proven to kill the bird flu virus and other harmful bacteria, viruses, and parasites.
But raw milk is a growing trend.
How long does bird flu persist in the unpasteurized, raw form?
It turns out, the bird flu virus can survive in raw milk under refrigeration temperatures (4° C) for at least eight weeks.
Bird Flu Can Survive Up to 8 Weeks at Refrigeration Temperatures
How about cheese made from raw milk? How long is bird flu in cheese detected?
The reason for the study is simple. “Highly pathogenic avian influenza H5N1 viruses have recently spread to dairy cattle, with high levels of virus detected in milk from infected animals, raising concern about the risk posed by unpasteurized dairy products consumed by humans,” said the Cornell University-led research team in a press statement.
The study was published in Nature Medicine in October 2025. The study was set up to determine how long bird flu in cheese is detected.
The cheese making process can vary from one type to another. Different aging processes, added ingredients, pH changes. All of the things that change the taste and texture of the cheese may impact the virus’s survival in the food.
The study looked at how long bird flu could persist in raw milk cheeses made with milk at three different pH levels. Those common to cheese making include pH’s of 6.6, 5.8, and 5.0 (with the lower number indicating a higher acidity). Additionally, different cheese products undergo an aging process. The study was designed around these variables.
In addition to H5N1 virus-spiked raw milk, commercial raw-milk cheeses found naturally contaminated with the virus were fed to ferrets to “evaluate virus infectivity.”
How infectious is the virus?
Existing aging requirements are imposed on raw milk cheese. Currently, raw milk cheese must be aged 60 days before allowed in commerce (in jurisdictions that permit its sale for human consumption).
This is significantly inadequate to reduce human exposure to bird flu in cheese.
According to the study, lower pH levels in raw milk showed infectious virus persisting throughout the cheese making process for up to 120 days for lower pH methods (6.6 and 5.8, but not 5.0).
“The current regulation requiring 60-day aging of raw-milk cheese before marketing proves insufficient to achieve HPAI H5N1 virus inactivation and guarantee cheese safety,” the authors explained.
There are, however, ways to reduce those risks. “Implementing additional mitigation steps, such as testing of raw milk bulk tanks or using milk pasteurization, thermization or acidification before cheese making, becomes crucial to ensure food safety.”
Most human cases of bird flu have been mild and in related to known exposure to sick or infected animals. However, some people have become very sick, requiring hospitalization. At least one person has died.
Mild symptoms of bird flu in people may include:
Less common symptoms may include diarrhea, nausea, or vomiting.
In some cases, people have developed moderate to severe illness.
Moderate to severe illness symptoms of bird flu in people may include:
Additional complications may include (but are not limited to):
People usually begin feeling sick around three days after exposure (two to seven days) with eye symptoms occurring a day or two sooner). It is unclear how long infected people are contagious. However, existing data says that people are most contagious within the first few days of their illness. Those with severe illness may be contagious much longer. High levels of the virus have been found in the lower respiratory tract for several weeks for those with pneumonia or other respiratory complications.
Alternatively, some people with bird flu in the United States have reported no symptoms at all. Unfortunately, there is not enough data to determine how common this occurrence is. Unfortunately, those without symptoms may still be contagious to others.
If you have become sick from bird flu in cheese or raw milk, there are a few things you can do to help your situation.
If you suspect you have bird flu, get medical attention right away. Early discovery of the virus may have more favorable health outcomes. Additionally, you may help investigators determine the source of a bird flu contamination or incident.
As soon as you feel well enough to do so, make a list of the foods you have eaten (where you got them and ate them) and places you have visited in the weeks prior to becoming sick. This information may help narrow or broaden traceback investigation activities.
If you have been negatively impacted by bird flu in cheese, it is a good idea to get advice from an experienced Food Poisoning Lawyer. A lawyer dedicated to these types of illnesses can answer questions you may have and even explain things you may not have considered.
If you wish to pursue a legal case, the dedicated Food Poisoning Lawyers at The Lange Law Firm, PLLC are here to help.
The burdens of foodborne illness add up. Lost work, medical bills, and other expenses may be recovered in a food poisoning lawsuit.
Call (833) 330-3663 or fill out the online submission form for a free, no-obligation consultation today!