With sporadic reports in recent weeks of cats infected with the coronavirus that causes Covid-19, a group of researchers set out to determine whether cats can transmit the pathogen to one another.

The answer, the scientists said: They can. The question now is whether felines can transmit SARS-CoV-2 back to people.

Researchers from the University of Wisconsin-Madison and the University of Tokyo noted that none of the cats in their study was visibly ailing, but they shed the virus from their nasal passages for about six days.

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“Considering the amount of virus we found coming out of the noses of the cats … there is the possibility that these cats are shedding, fomites are being released in a person’s household or at cat shelters or human societies and that somehow people could possibly pick up the virus. I think it’s something people should be aware of,” said Peter Halfmann, a research professor at the University of Wisconsin and first author of the study, published as a letter in the New England Journal of Medicine.

“It depends on the household and the cat, but there could be a lot of close contact with your pet cat on occasion,” Halfmann said.

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The researchers, led by virologist Yoshihiro Kawaoka, experimentally infected three cats, and then placed an uninfected cat into each of the cages housing the infected animals a day later. The three uninfected cats were all infected within five days.

Halfmann said uninfected cats were also put into cages a foot away from the cages containing the infected cats. None of those felines became infected with the virus.

In early April, Chinese researchers reported that cats and ferrets were susceptible to infection. A few weeks later the U.S. Department of Agriculture announced that two pet cats in New York state had tested positive for the virus. At least eight big cats at the Bronx Zoo — tigers and lions — were also infected with the virus.

Many research groups have reported on virus shedding with Covid-19 by simply conducting testing by polymerase chain reaction, or PCR. A positive PCR hit tells you that the human or animal is shedding something, but it doesn’t reveal if they are emitting viral debris — which poses no risk of infection — or actual infectious viruses.

The researchers responsible for this work did attempt to grow viruses from swabs taken from the noses and rectums of the cats; they found that all the animals were emitting infectious viruses from their noses. None of the rectal swabs produced infectious virus.

Halfmann said there was quite a lot of virus — between 30,000 and 50,000 virus particles per swab. But what that means isn’t clear, he said. It’s not known how big a dose of virus is needed to infect a person. And there’s no ethically acceptable way to construct a trial to see if cats can infect people.

Still the researchers suggested people should be aware of the possibility of transmission from cats to people, and keep cats away from anyone in a household who is suspected of being sick with Covid-19. “I think it’s good practice to have this in people’s minds,” Halfmann said. He and his co-authors also urged people not to abandon cats or give them up for adoption because of such concerns.

They also advised cat owners to keep their cats indoors.

“Cats are still much more likely to get Covid-19 from you, rather than you get it from a cat,” Keith Poulsen, director of the Wisconsin Veterinary Diagnostic Laboratory, said in a statement.

  • It is OBVIOUS that people are giving it to cats. Cats can NOT swim across the ocean… Duh.

    What worries me is the panic this will create and people will get rid of their pet cats.

    I was deeply disturbed reading how they purposefully infected cats. I hope that they cared for these animals and did NOT just murder them after the experiment.

    People are capable of evil intentionally. Animals do not possess the intent of evil. Animals (if anything) love us unconditionally.

    There was NO disclaimer that people should NOT ABANDON their cats. Shame on @HelenBranswell. People have never failed to provide me with reasons to have disdain for my fellow man.

    Some like Teresa p Collins do give me hope. No animal has ever given me a reason for disdain of them.

    PLEASE DO NOT GET RID OF YOUR CATS.

    • A person from a local shelter mentioned to my wife that people are currently terrified of taking in cats right now.

      In an attempt to get people to take the disease seriously, the government and the media have fanned the flames into an extreme, irrational panic. I was working in a store during the Hong Kong flu. The store never closed. Customers and employees went about business as usual.

  • So, another silly experiment where animals are artificially infected in a lab. I am still waiting to see a real-world situation where virus from a supposedly infected nonhuman animal is positively determined to be SARS-CoV2, and not one of the many very similar coronaviruses known to infect cats, dogs, and other animals. Interesting, too, that this blurb immediately follows the one noting that some of the tests for humans may be accurate only half the time. Hmmmm. So, how accurate are the tiger tests?

  • Livestock (cattle, pigs, and chickens) get non-COVID-19 coronaviruses. There is even a coronavirus vaccine for cattle. The question is, can livestock, like cats and dogs, get COVID-19 and, if so, can they infect meat processing facility workers via respiratory and fecal-oral transmission. The only way to know is by testing the livestock in meat processing facilities struck by COVID-19.

  • The initial response in the pandemic was to drop this risk of transmission between people, to drop the R-nought to less than 1. The idea was to hold that R-nought to less than 1 and expect the virus to die out, naturally. This strategy worked for SARS. And, yet, we can see from countries that had an optimal response to the virus, this strategy did not work. Cases are occurring in Germany and South Korea. Why? I believe cats play a bigger role as an animal vector than we are prepared to admit. The US is home to millions of feral cats. Since we know infected house cats can spread that infection relatively easily, has anyone thought to check feral cats. Your outside cats can, and does, have contact with feral cats.

    • ” drop this risk of transmission between people, to drop the R-nought to less than 1. …”

      That made some sense when it was thought that the reported cases represented the majority of infected people. Now estimated numbers in the US are running toward 30 million, and possibly more, many unaware that they have or have had the disease. With numbers like that chances of lowering the r0 through a general lockdown is essentially zero.

      Several mathematical researchers (including a paper from a researcher at Woods Hole) have failed to find any strong evidence (changes in slope of the curves etc that should have been a marker) that the lockdowns actually changed things much. What we’re seeing is the normal progression of an epi/pandemic.

  • I have 10 cats they never go outside and I worry a lot about me giving or carrying Covid to them. Not once have I worried about them giving it to me nor would I worry about that. I really hope people do not take this article out of proportion and get rid of their cats. I would never consider getting rid of any of them and hope they will all be fine.

  • In the case of the Bronx Zoo, it would be hard to imagine caretakers getting closer than ‘social distancing’ contact with those animals. Not sure what that says about the practicality of our current regulations.

    • Social distancing is not the only preventions for Covid-19. Likely the Big Cats got infected as their handlers touched food, water, gates, doors, etc and cleaned out cages. If research proves that cats can infect humans (they are often lap-animals, get cuddles, are held close to faces, etc) then what is missing in this article is that people who take in / take care of strays should be warned to stop that good-samaritan activity.

  • Interesting, although I doubt cats will ever become a significant factor in spreading SARS-CoV-2 around the planet. It would pose questions only for the households of victims which must decide whether to allow pets access to the sick person, and even then I’d expect other household members to face much more risk from direct transmission than through their cat.

    I agree keeping cats indoors unless on a leash is safer, for many reasons besides Covid. Loose cats have a way of returning home with notches taken out of their ears in fights with rivals, not to mention getting hit by cars.

    • I think a free wandering cat has a good chance of getting infected by another cat, then bringing the disease into it’s household, infecting the people there.
      Unlike some other animals, cats lick themselves constantly, and so, their fur will be full of virus. People will pet them and get the virus on their hands. It appears the cats can often by asymptomatic or nearly asymptomatic, so the humans will not suspect there is a risk.

  • The cats shed a lot of virus but no one is willing to say if cats can infect humans?
    OK, I will go out on a limb and say, Yes, if they shed a lot if virus, they can infect you.
    And further, though the sample is small, the cats so far do not seem to get sick enough to be identified as a hazard.
    One report from Wuhan said 11% of cats there were infected. For all we know they carry it a long time and spread it to many other creatures.

  • I think we humans are infecting felines. In the Bronx zoo case the keeper was diagnosed with the virus and still he continues caring for the tigers .
    The firts case in NY. The pet owner contracted the virus and his cat that has been very healthy, became sick, after his owner was recovering from the virus.
    We humans selfishly damage nature and animals . Very sad.

    • Really, nature seems to damage humans on a regular basis.

      Hiv from Chimps, MERS‐CoV from dromedary camels, fleas and lice spreading the black plague, Covid likely from bats, etc, etc.

      Zoonotic diseases are legion.

      I wouldn’t go so far as to say, nature and animals are being selfish, but nature/animals do seem to get their own revenge, though I wouldn’t subscribe such traits as selfish or revenge, it’s just the way life is.

      I strongly suspect cats can infect humans, though doubt it’s very common, the majority of cats in the USA stay in the home, I seldom see free ranging cats.

  • I think we humans are infected felines. In the Bronx zoo case the keeper was diagnosed with the virus and still he continues caring for the tigers .
    The firts case in NY. The pet owner co tracked the virus and his cat that has been very healthy, became sick after his owner was recovering from the virus.
    We humans selfishly damage nature and animals .

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