Bird Flu in cats raises new worries about human risk

It’s a real-life version of the old Sylvester and Tweety cartoon — except when the cat catches the bird, the danger doesn’t end there. Bird flu, or avian influenza, has killed more than 166 million birds nationwide. While chickens have been the hardest hit, the virus is now infecting other animals — including dairy cattle and, more concerningly, domestic cats.

A new study from the University of Maryland’s School of Public Health warns that bird flu infections in cats could help the virus adapt to mammals, including humans, raising fears it could eventually spark a future pandemic. The study was published in the journal Open Forum Infectious Diseases.

“The virus has evolved, and the way that it jumps between species — from birds to cats, and now between cows and cats, cats and humans — is very concerning. As summer approaches, we are anticipating cases on farms and in the wild to rise again,” said senior author Dr. Kristen Coleman, an assistant professor in UMD School of Public Health’s Department of Global, Environmental and Occupational Health, and affiliate professor in UMD’s Department of Veterinary Medicine.

USDA reports higher rates of cat infections nationwide

Unlike routinely tested cattle, researchers aren’t monitoring cats for bird flu, even though they often live close to people. Infections are rising, especially among outdoor and farm cats, with most cases linked to eating infected birds, milk from infected dairy cows or raw chicken feed.

The U.S. Department of Agriculture (USDA) has reported 126 cases of bird flu in domestic cats since 2022, about half of them in the past year.

In February 2025, Tim Hanson of Portland, Oregon, said his cat became sick after eating premium raw pet food. “It was finely ground to a consistency that I thought was beneficial to my cats,” he said. After the cat developed a fever and stopped eating, a test confirmed bird flu. He ultimately had to put her down. That same month, New Jersey confirmed its first case of bird flu in a cat, following similar reports in other states.

Officials have reported cat infections worldwide, including in Finland, France, Poland, Italy, Peru, South Korea and the U.S., often in zoos, animal shelters or rural areas.

Why are cats hit harder than other mammals?

Dogs have had far fewer cases, and while nearly 1,000 dairy herds have tested positive, cattle tend to show only mild illness. Scientists are working to understand why cats are hit harder than most mammals. 

The American Veterinary Medical Association suggests cats are especially vulnerable to H5N1 bird flu because they frequently hunt birds and can also be exposed through raw meat or milk. Research also shows that cats have receptors throughout their bodies that make it easier for the virus to spread, often leading to serious infections.

“Bird flu is very deadly to cats, and we urgently need to figure out how widespread the virus is in cat populations to better assess spillover risk to humans,” said Coleman.

Only a few genetic mutations away

So far, there are no confirmed cases of bird flu spreading from cats to humans. Human infections are rare and usually result from direct contact with infected animals. Symptoms can range from mild to severe, and some cases have been fatal.

While the virus has never spread from person to person, experts warn that just a few genetic changes could make that possible. That’s why public health officials, veterinarians and pet owners are being urged to keep a closer eye on cats.