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The H5N1 avian influenza virus, commonly called “bird flu,” is striking dairy farms across the nation and in our home state of Vermont. More than  have been affected in the U.S. since the disease arrived in 2016, according to the Centers for Disease Control. The virus also shows signs of mutating to become more infectious to mammals and is being detected in more dairy herds, which could impact Vermont’s dairy and agriculture industries.

We spoke with Peter Hyson, M.D., assistant professor of medicine in the Division of Infectious Diseases, Department of Medicine, and Emily Bruce, Ph.D., assistant professor in the Department of Microbiology and Molecular Genetics, at the Robert Larner, M.D. College of Medicine about what Vermonters in particular should know about the disease. 

1. What is ‘bird flu’?

Bird flu, also called avian influenza, is a viral infection that primarily affects birds but can also infect humans and other mammals. The current bird flu outbreak in the U.S. is caused by the H5N1 subtype of influenza, which is a type of influenza that has historically caused a high level of illness and death in both poultry flocks and people who became infected. Currently, there are large outbreaks among wild bird populations, as well as poultry, such as chickens raised on both commercial farms and in backyard flocks, and among dairy cows. The virus can also infect cats and other animals that may have contact with people.

2. How many people have been infected so far?

Sixty-nine Americans have been infected with bird flu since 2024, and one person has died. It is very likely, however, that this number is an undercount of the true number of human infections, due to difficulties in testing everyone who may have been infected. Since 2003, there have been 954 confirmed cases of human infection with avian influenza (H5N1), and in 464 of those cases the infected person died. 

3. How have people become infected?

People can get infected when they get droplets containing live bird flu virus in their eyes, noses, or mouths or when they breathe particles or dust containing the virus. We know that raw cow’s milk from infected animals can contain extremely high levels of the virus, and so can urine and feces from infected birds. Most of the people who have been infected are farm workers exposed to cows or chickens sick with bird flu. So far, there is no evidence of person-to-person spread of this virus. 

4. How does this impact Vermonters?

Bird flu has been recently detected in a backyard flock of noncommercial birds in the state of Vermont as well as in wild birds throughout the state, but so far there has not been detection of the virus in humans, cows, or commercial birds in Vermont. Raw milk in the state is being monitored for presence of the flu virus. While we are fortunate that there have not been widespread outbreaks in Vermont agricultural facilities, millions of infected birds have been culled in farms across the country, which is contributing to the rising cost of eggs nationwide. There have been three independent introductions of avian flu into dairy herds in the U.S. in a little over a year and many outbreaks in poultry, so this is a situation that could worsen quickly.

5. With Vermont's large farming communities, should people be worried about eating poultry, eggs, and even beef?

Fortunately, milk pasteurization and ordinary food preparation (fully cooking eggs, beef, and chicken) kills the virus. There is no evidence that anyone in the U.S. has gotten sick from eating infected eggs or meat; however, there have been human cases in other countries linked to consuming undercooked poultry. Several cats have died after consuming raw milk that contained H5N1 virus, but standard commercial pasteurization effectively kills the virus—so it’s important not to drink raw milk or feed it to pets.

6. Who is at risk of being infected?

Currently, people who work with animals (especially dairy cows or poultry) or close to animals (including dead/ill wild birds) are at the highest risk. This is because the virus is not yet able to spread from one infected person to another. If the virus does gain the ability to move between people, the risk to the general public will increase. Each time a human is infected with H5N1, the risk increases that the virus could mutate to be able to spread from one person to another. Lowering the number of infections in farmed animals and the people who take care of them is an important step in preventing community spread.

7. How do you know if you’re infected?

Symptoms of bird flu infection are similar to those of standard flu and include cough, sore throat, headache, fevers, chills, and/or body aches. A lot of the people who have been infected with bird flu have had conjunctivitis (commonly known as “pink eye”), which is eye redness, irritation, and itchiness. Standard flu can be diagnosed with a swab of the back of the nose and throat at your doctor’s office or even with a test bought over the counter at a pharmacy. If you have flu symptoms and/or conjunctivitis and/or you think you may have been exposed to infected animals or animal products, then your doctor can do a swab of your nose, throat, and eyes and send it to the Vermont Department of Health (VDH) to check for bird flu. Anybody hospitalized with influenza A at �պ����� will automatically have testing sent to the VDH to check for bird flu. If you think you or someone you know needs a test, contact your doctor or call the VDH epidemiology line at (802) 863-7240 or 1-800-640-4374 (available 24/7).

8. How can people protect themselves? 

If you work with animals (especially poultry, wild birds, or dairy cattle) and have symptoms of avian influenza (flu-like symptoms or conjunctivitis; i.e., itchy, red eyes) you should contact your primary health provider or the Vermont Department of Health to get tested for avian influenza. If you see sick or dead animals (including wild birds or mammals), you should wear personal protective equipment (gloves, mask, goggles) before handling them—only if necessary—and contact the relevant authorities (e.g., the Vermont Agency of Agriculture or the United States Department of Agriculture). For the general public, getting your influenza vaccine is important to reduce the circulation of seasonal strains of influenza and to help keep you healthy. It’s also very important not to drink raw milk, and to cook your eggs and meat to recommended temperatures before eating them.

9. Where can people find more information?