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Pets can be vulnerable to catching the flu from their human companions.

People can give the flu to their pets

by Mitch Smith
Oct 04, 2012

Mac had all the symptoms of the flu.

The teenager was coughing, sneezing and wouldn't eat. Two people in his household had come down with H1N1, the pandemic flu that swept across the world in 2009. So doctors tested Mac and determined that the 13-year-old Iowan was also infected.

That wouldn’t have been surprising if Mac had been a person.

But Mac was a domestic short-haired cat. And the idea of companion animals catching diseases from their owners is not well-understood.

Veterinarians call the process reverse zoonosis, and American researchers have counted more than a dozen of these human-to-pet infections stemming from the H1N1 virus. Mac survived, but many other pets did not.

Dr. Jessie Trujillo, an Iowa State University veterinarian and microbiologist who has studied reverse zoonosis, said there’s no evidence that people can catch the flu directly from an animal even if that animal contracted the disease from a human. But much about the phenomenon remains unknown.

Until scientists learn more about reverse zoonosis, Trujillo suggests caution in mixing animals and people who are ill.

“If you’re sick, the recommendation is that you should probably stay away from people and animals,” she said. “If you’re sick and your animal becomes sick and you need to take it to the vet, you should probably have someone else take it.”

People shouldn’t panic or get rid of their pets, she said. But they also shouldn’t assume they are in the clear because the H1N1 pandemic subsided.

“Even though people say the pandemic is over,” Trujillo said, “this virus emerged and persists in the population and is continuing to persist in the population.

“There’s something very unique about this particular virus. Once it gets very high in people, there’s at least a documented possibility that there’s a susceptibility in companion animals.”

Reports of reverse zoonosis in companion animals were largely anecdotal before H1N1, Trujillo said.

Now she and colleagues at Iowa State and Oregon State universities are studying several recent reports of cross-species infection, including a sick cat in New York and infected ferrets in Oregon, looking for clues about how and why reverse zoonosis happens.

“We just really don’t have an idea whether we’re going to see a significant amount of infection in animals,” she said. “There’s a lot of the things that are unknown.”

Martha Cannon, a volunteer with the Greater Chicago Ferret Association, said her seven ferrets contracted flu-like symptoms when she was sick a few years ago. The animals weren’t ever diagnosed, but Cannon believes they contracted the illness from her.

“I came down sick with sneezing and coughing, and they all had to go on antibiotics for a couple weeks,” she said.

Cannon said the risk of human-to-animal transmission is recognized among ferret hobbyists, which is why ferret association volunteers are asked to stay home when they’re sick.

But avoiding animals when ill can be hard. Many flu patients recuperate on the couch, sipping tea and watching reruns of “The Price is Right” with their pets. Just like Mac, Trujillo said, most cats want to comfort their ill owners.

“When people get sick,” she said, “cats want to stick around you, which is really difficult because you’ve got to shoo them away.”