How to protect your pets from bird flu

A subtype of avian influenza, known as H5N1, continues to spread among wildlife, dairy cows, domestic birds, and some pets in a string of global outbreaks that began in 2020. The highly pathogenic virus was first detected in U.S. wild birds in 2022, and has since led to the culling of more than 166 million poultry  and infected nearly 1,000 cattle herds. This strain has also infected hundreds of other mammals nationwide, according to data from the U.S. Centers for Disease Control and Prevention. 

Since 2022, there’ve been 70 confirmed human cases in the U.S., largely among farm workers. One person died in Louisiana after an infection resulting from exposure via a backyard chicken flock. There are no documented instances of human-to-human spread and the CDC currently considers the risk to the general public to be low. 

Yet the virus has stoked fear and uncertainty–most recently among pet owners and veterinarians as house cats emerge among the casualties of the ongoing outbreak.

“We are hearing concerns from our doctors. People are asking and people are worried,” Sandra Faeh, a veterinarian and president of the American Veterinary Medical Association (AVMA), tells Popular Science. 

How to understand the risks to pets

As of March 6, more than 100 domestic cats have been infected since 2022. Wild cats like lynx and captive tigers have also fallen ill. Considering the tens of millions of pet and stray cats in the U.S., confirmed cases remain exceedingly rare. “Just like in humans, the risk of pets contracting H5N1 is relatively low” outside of farm settings, says Peter Halfmann, a virologist at the University of Wisconsin-Madison, School of Veterinary Medicine. 

However, H5N1 is a severe and often a deadly virus for felines. “The strain that’s currently circulating has a near 90 percent case fatality rate in domestic cats,” Kristen Coleman, an infectious disease researcher at the University of Maryland, tells Popular Science. That’s based on Coleman’s own research of bird flu infections among cats, which has not yet been peer-reviewed. 

Symptoms for cats vary, but often include loss of appetite, fever, and lethargy. Cold-like symptoms such as runny nose and eye gunk might also appear. Neurological signs are also common, and a cat infected with bird flu may seem disoriented, experience tremors, or repeatedly circle. “If there’s something off, call your veterinarian,” Faeh urges. 

Dogs and other other pets can also become sick with H5N1. While there have been no reported cases among domestic dogs in the U.S. during this outbreak, one pet dog fell fatally ill in Canada in 2023 after chewing on an infected goose carcass. Pet birds are theoretically susceptible to the virus, the same way that wild birds are. Rodents like mice and rats have tested positive. Wild rabbits can also be infected, and so it’s probable that many small pets are technically at risk. 

Yet, aside from poultry and cattle, pet cats have proven to be the domestic animals most vulnerable to the virus. The reason is likely the result of both behavior and biology. 

Why are cats so vulnerable?

First, H5N1 may be more adept at infiltrating and replicating in feline cells than those of other mammals, Coleman explains. “There could be something unique about their anatomy and physiology that’s different, and we don’t know exactly what that is.”

Avian influenza is primarily evolved for bird hosts and is particularly fast-spreading and virulent among poultry and waterfowl. Its ability to infect mammals depends, in part, on the presence or absence of a certain type of cell receptor that birds have. The disease presentation and severity can change depending on which tissues contain that receptor. Cows, for instance, have high concentrations of avian-like cell receptors in their udders, though not their lungs. That’s likely why the virus has been able to spread through milking equipment, why cows haven’t shown typical respiratory symptoms with the illness, and why cows have been shedding so much virus in their milk.

Cats carry receptors for both avian and human influenza viruses in their airways, Coleman notes. This means cats could become infected with both bird and human flu at the same time, serving as a petri dish for a dangerous viral admixture. It’s the same reason epidemiologists are often specifically concerned with swine outbreaks, as pigs share the same trait. Dogs also have receptors for H5N1 in their respiratory tract. However, receptors don’t tell the whole story, and there are other molecular factors at play, like replication rates inside cells. Differences in genetics or immune response may play a role in cats’ particular susceptibility, says Halfmann.  

Cats also likely face increased risk because of their lifestyle. Compared with dogs, pet cats are much more frequently allowed outdoors with little supervision, and cats are prone to hunting and scavenging. 

How are pet cats getting exposed?

In prior bird flu outbreaks, there’ve been several documented cases of feline-to-feline spread, but ingestion seems to be the primary route of exposure for pets in the current outbreak, says Coleman. If an outdoor cat catches an infected bird or rodent, that can make them sick. 

Exposure to raw milk or uncooked, infected meat is also a major risk factor. On farms, cats may have inadvertent access to unpasteurized milk, leading to feline illness. Off farms, some pet owners opt to feed their animals raw dairy and meat products. The AVMA never recommends raw diets for dogs or cats because of the risk of multiple pathogens. The spread of H5N1 makes this practice increasingly risky, Faeh says. 

Earlier this month, pet food company Wild Coast LLC expanded an earlier recall of a raw cat food product. The recall was initially issued in February after several pet cats in Oregon became severely ill and were ultimately euthanized. Tests confirmed a container of Wild Coast Raw Boneless Free Range Chicken Formula cat food in the household was positive for bird flu. Since then, the company has widened their recall net to encompass more products. At least two other raw pet food products from two different companies (Monarch Raw Pet Food and Northwest Naturals) have been linked to cat deaths in the last 15 months. 

Contact with dead animals even without ingestion, feces from infected animals, or contaminated surfaces and objects (called “fomite”)  may also be sources of infection, says Faeh. One recent CDC report documented two instances of fully indoor cats becoming infected in households of dairy workers where the humans themselves didn’t report symptomatic illness. It’s possible that the cats were exposed via shoes or clothes. Fortunately though, all of the above factors are within pet owners’ control. “There are things we can do to help mitigate the risk,” Faeh says.

How to keep your pets safe

First and foremost, Coleman says to reconsider feeding your cat or dog raw milk or raw meat: “My suggestion would be to wean them off of a raw food diet for now.” If pet food testing requirements are put into place, then raw foods may become safer in the future, she adds. 

Second, limit your cat’s outdoor time. If there are known outbreaks in your area among wildlife or farms, keeping your cat inside (or at the very least supervising them while outside) is the best bet to minimize infection risk, says Faeh. “If you have a cat that’s used to going outside, it’s going to be a little bit of a challenge. Try walking them on a leash, some cats do tolerate that really well. If you can’t do that, stimulate their environment inside,” she suggests. 

As bird flu has been detected in mice and rats, it’s an especially good time to work on controlling and preventing the entry of rodents in your home. 

If you have backyard poultry, instituting biosecurity measures can help prevent illness in both your birds and your other animals. Flock owners should try to keep the poultry area covered, to reduce the risk that passing wild birds might stop by or poop in the area. Poultry keepers should also minimize the amount of other human and animal traffic their birds are exposed to, Faeh says. 

Those with backyard chickens or waterfowl should change out their clothes and shoes after working in the coop or bird run to avoid potentially bringing pathogens into the house, says Halfmann. “Have a separate pair of clothes that you switch out.” He also recommends wearing a mask when doing dirtier tasks like shoveling out old bedding material. Thoroughly washing your hands or using a 70 percent hand sanitizing gel after any animal exposure is always a good idea, he adds. 

If you see a sick or dead bird–wild or domestic–contact your local Department of Natural Resources or USDA agent, and follow official guidelines on proper reporting and disposal. Ultimately, protecting your pets from bird flu also protects you. In a past outbreak with a closely related avian influenza virus, at least one human infection was traced to a sick cat. In the current outbreak, a cat may have passed the virus onto a teenager in the same household. The fewer chances the virus has to infect new hosts and intermingle among species, the better for us all–human and animal alike.

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