As of February 2025, over 166 million birds have died or been killed by the highly pathogenic avian influenza (HPAI) since the virus first appeared in the United States in 2022. And the H5N1 bird flu virus has spread to all 50 states.
Recently, as the price of eggs continue to increase due to a resurgence of the bird flu in commercially farmed laying hens, the H5N1 virus has returned to the headlines. The reason scientists worry about avian influenza or, ‘bird flu’, is because in all four influenza pandemics in recorded history, starting with 1918 ‘Spanish Flu’, the influenza viruses responsible contained at least one genomic segment that was derived from a bird virus.
H5N1 viruses have been circulating among birds and poultry since the late 1990s, but a current form of the virus called 2.3.4.4b is particularly good at transmitting between wild birds and poultry, resulting in an unprecedented number of deaths in many parts of the world. It is also increasingly triggering outbreaks in mammals, including mink, foxes, seals, otters and cats.
Since the U.S. outbreak of avian influenza A in dairy cattle began in March 2024, dozens of cats are known to have contracted the virus, including barn and feral cats, indoor cats, and big cats in zoos and in the wild (e.g., mountain lions, tigers, leopards, and bobcats). Cats were already known to be susceptible to the H5N1 virus, with several feline cases linked to poultry or wild bird exposure before the outbreak in cattle began.
Cats appear to be particularly susceptible to this severe illness, often resulting in death. Whether infected cats can infect other cats is currently unclear; however, that possibility cannot be dismissed. The risk of cat-to-human transmission is considered extremely low, but may increase with prolonged, unprotected exposure to infected animals. Whether direct human-to-cat transmission can occur has not been established, although a recent report of H5N1-infected cats in the households of two dairy farm workers suggests this is possible.
The good news is that infection can be prevented with a few simple practices.
While house cats are not wild animals, and most veterinarians advise against feeding companion animals raw food because of pathogens like salmonella and listeria.
Recent investigations implicate food as a source of infection for cats, most often unpasteurized milk and raw or undercooked meat (e.g., poultry). Other potential sources include:
- Raw colostrum and other unpasteurized dairy products (like cream)
- Exposure to infected wild birds or poultry
- Exposure to infected livestock and their environments
- Exposure to people who work on affected farms and to their clothing or other fomites
Since 2022, more than 70 cats have contracted H5N1. Dr. Jane Sykes, who specializes in infectious diseases in cats and dogs at the University of California-Davis School of Veterinary Medicine, says that many were barn cats and drank milk from infected cattle: A study published last summer found that about half of the infected cats on a dairy farm in north Texas died from the virus.
Last month, the Oregon Department of Agriculture said that a house cat contracted the virus and then died after consuming a frozen turkey product made by raw pet food brand Northwest Naturals. It stated that “tests confirmed a genetic match between the virus in the raw and frozen pet food and the infected cat.”
Northwest Naturals voluntarily recalled this batch of its frozen turkey-based product. The company told NPR that the recall involved “a small product run” and it has concerns about the accuracy of Oregon’s Department of Agriculture’s testing.
Also last month, Los Angeles County’s public health department confirmed two cats tested positive for bird flu after drinking raw milk from the Raw Farm dairy in California’s Central Valley. Raw Farm voluntarily recalled its milk and cream after retail products tested positive for H5N1, but it denies any food safety issues, calling the concern “a political issue.”
After these and other instances of sickness among house cats, the U.S. Food and Drug Administration announced last week it is now requiring cat and dog food companies to update their safety plans to protect against bird flu.
Vets say the safest bet is conventional pet food. Dr. Bruce Kornreich, the director of Cornell University’s Feline Health Center, says he isn’t worried about the possibility of H5N1 in these since heat used in cooking, canning and pasteurization seems to neutralize the virus.
Any cat that spends unsupervised time outdoors is at risk of catching bird flu, warns Dr. Michael Q. Bailey, the president-elect of the American Veterinary Medical Association.
The main concern is when kitties hunt, they’ll prey on infected songbirds or rodents, especially mice.
Bailey recommends that people watch out for signs of lethargy, runny nose, or discharge around the eyes. Illness may start with loss of appetite, lethargy, and fever, then quickly progress, with cats exhibiting:
- Neurologic signs (e.g., imbalance, circling, tremors, seizures, or blindness)
- Severe depression
- Heavy discharge from the nose and eyes
- Other respiratory signs: rapid or difficulty breathing, possibly sneezing or coughing
If a cat does seem sick, Sykes says people shouldn’t assume it’s bird flu — even if their animals spend time outdoors or eat a raw diet. Upper respiratory illnesses are common in cats, while H5N1 is “still pretty rare.”
Bird flu can cause neurological symptoms such as dizziness and seizures, which are symptoms of rabies, too. Rabies is almost always fatal, and it poses a threat to human health, so any animal suspected of having this virus must be euthanized.
While bird flu in domestic cats is fairly rare, it also seems that cats appear to be dead-end hosts for this virus, meaning they can’t pass it to other animals or people. There’ve been no known cases of cat-to-human transmission during the current outbreak of H5N1. The American Veterinary Medical Association says chances of this occurring are “considered extremely low, but not zero.”
Most people who get H5N1 have been farm workers in direct contact with infected poultry or cattle. Of the 67 confirmed human cases of H5N1 in the U.S., there’s been just one fatality. The strain of bird flu currently circulating has not adapted to easily infect humans or spread among us.
Still, bird flu viruses mutate over time, cautions Sykes.
So, when house cats get sick with H5N1 and then cuddle up to their people, this creates more opportunities for bird flu to potentially adapt to a human host.
The more cats that eat raw food, the more chances for an infection and a species crossover event to occur, says Ian Gill Bemis, a Ph.D. student who studies avian influenza in cats at the University of Maryland Department of Veterinary Medicine and the School of Public Health.
“I think there is a significantly high risk to public health that humans might become infected if large numbers of people are feeding their cats raw food at this particular point in time.”
– Ian Gill Bemis, Ph.D
There is at least one instance of a cat infecting a human with another kind of bird flu, called H7N1. As NPR reported in 2016, a veterinarian in New York City caught the virus after having close contact with infected cats. She experienced mild symptoms and quickly recovered.
Sykes says that this 2016 bird flu virus is very different from H5N1. But it’s an example that cat-to-human transmission is possible with avian influenza.
Every cat owner wants to do what’s best for their cat, and that means taking care of themselves as well.
