Over the past few months, an outbreak of avian influenza has spread rapidly among dairy cows in the United States, infecting more than 90 herds in 12 states. Along the way, the virus has caused collateral damage to several other species, spreading from dairy farms to poultry farms and from cows to at least three farm workers who developed mild symptoms of the disease. It has also caused an increasing number of cat deaths.
On some dairy farms, sick or dead cats provided an early sign that something was wrong. “It’s kind of like canaries in a coal mine,” Kammy Johnson, a veterinary epidemiologist with the Department of Agriculture, said at a briefing.
Since the outbreak was first detected among cattle in late March, at least 21 cats in nine states have contracted the virus, according to the department, which only recently began monitoring feline cases. Scientists have long known that cats are vulnerable to infection with avian influenza, a group of influenza viruses typically found in birds.
In 2020, a new version of the bird flu virus, known as H5N1, emerged and has spread rapidly around the world, infecting many wild birds and steadily spreading to some mammals, such as cats. “Domestic cats are actually very susceptible to bird flu, especially the H5N1 virus,” said Kristen Coleman, an infectious disease researcher at the University of Maryland. “But there has been a recent uptick in domestic cat infections — a dramatic uptick.”
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There have also been sporadic reports of infected dogs. While bird flu infections in pets remain rare overall, they can be serious, especially in cats. “They cause very severe illness and often death,” Coleman said. “So it’s very dangerous and needs to be taken seriously.”
However, there are some “reasonable precautions” that can help people keep their pets safe, Coleman said. Here’s what to know:
How do cats get bird flu?
On dairy farms, cats became infected by drinking unpasteurized milk from sick cows, also known as raw milk, which can contain very high levels of the virus. More than 80 percent of the affected dairy farms had cats on their premises, and more than half of them reported sick or dead cats, according to federal data released Thursday. But even before the recent outbreak in cows, there were reports of infected cats, some of which likely contracted the virus by feeding on infected birds.
“As more dead wild birds become available, if there are more dead poultry, these carnivores that can access and ingest them are going to get a huge dose of the virus even if they find them dead,” said Justin Brown, a wildlife veterinarian at Pennsylvania State University. Some larger outbreaks have also been linked to contaminated raw poultry. For example, in 2023, an outbreak of bird flu hit two cat shelters in Seoul, South Korea. Government investigators later discovered the virus in raw duck meat that was fed to the cats.
How does bird flu affect cats?
Cats infected with the virus often become seriously ill, and in some cases the mortality rate has been “shockingly high,” according to Younjung Kim, a veterinary epidemiologist at France’s National Institute of Health and Medical Research. Kim said that at one affected shelter in South Korea, 38 of 40 cats had died.
In a recent review, which has not yet been published in a peer-reviewed journal, Coleman found that the new version of H5N1 had a 67 percent fatality rate in felines. (That estimate is based primarily on domestic cats, though it includes a handful of cases in other species, such as lynxes and bobcats.) Many infected cats develop fever, loss of appetite and respiratory symptoms, which can include a runny nose, difficulty breathing and pneumonia.
Neurological symptoms such as stiffness, tremors and seizures are also common. “It is sometimes confused with rabies,” Coleman said. Cat infections can also be asymptomatic, although it is unclear how common this is, as mild or asymptomatic cases may go undetected.
Are dogs also in danger?
Yes, there have been a handful of cases in dogs, including severe cases. In the spring of 2023, a dog in Ottawa, Ontario, contracted the H5N1 virus and died “following chewing on a wild goose,” according to the Canadian Food Inspection Agency.
That same year, an infected dog in Poland developed a severe cough and other symptoms but recovered. However, overall, dogs appear to be less susceptible to the virus than cats and seem less likely to develop severe disease.
How can I protect my pet from bird flu?
According to experts, pets kept indoors should be at extremely low risk. However, owners should avoid feeding their pets raw milk or raw meat, both of which can transmit the virus. Of course, many pets’ lifestyles make it impossible to spend all their time indoors. “We’re not asking you to lock your pets up,” Coleman said.
Experts recommend that owners take common-sense safety measures for pets that spend time outdoors, such as trying to keep them away from sick or dead birds and places where wild waterfowl congregate.
Removing shared food and water sources, such as bird feeders and baths, can also help slow the spread of the virus.
