I’ve done countless presentations and interviews about COVID and animals, and the question of whether pets can infect people always comes up.
My general line has been “We know that human-pet infection is pretty common. My main concern is cats, since we know they can spread it cat-to-cat. If they can do that, it’s logical to think they could spread it cat-to-person. However, it will be tough to sort out. If a cat is infected, it almost invariably got it from someone in the household, and figuring out whether it was the cat or the infected person infected someone else in the household or a visitor is almost impossible. The main way we’ll figure that out is if we see evidence of transmission in a vet clinic or shelter, where there’s not linked human-human spread.”
A paper in the upcoming edition of Emerging Infectious Diseases (Sila et al) rounds out this discussion, as they provided strong evidence of cat-to-vet transmission.
The story involves a 32 yr old veterinarian, two people with COVID, and their cat.
Those two owners had severe COVID and were taken by ambulance on a 20hr trip to the nearest available bed. They had a cat and (I’d love to know how this came about) it rode along in the ambulance.
Upon arrival, the owners went to an isolation unit for treatment and the cat was sent to the university veterinary hospital, where it was examined by the vet (and two colleagues).
The cat was healthy and she collected nasal and rectal swabs for SARS-CoV-2 testing. During the process, the cat sneezed in her face. She was wearing an N95 mask but not eye protection (a common lapse. If we have a high risk scenario where we need an N95 mask, eye protection is almost always indicated. As a profession, we do a pretty bad job of that, though.)
Anyway, I’m not sure how concerned they were at the time. The cat wasn’t known to be positive and getting sneezed on by a cat isn’t exactly a rare event for a vet (neither is getting drooled on, puked on, pooped on or close encounters with pretty much any bodily fluid….occupational hazard).
However, 3 days later, the vet started to feel sick. She didn’t seek medical care until the results of the cat’s test came back 2 days after that….positive. She was tested and was positive.
The timing is bang-on for cat-human infection, but we need to investigate situations like this further, since unknown exposure to another person has to be considered. A vet in the hospital’s large animal clinic also got COVID around the same time, but there was no known contact between them and she didn’t report any other known contact with an infected person.
Here’s where genomics come into play. When they sequenced the virus from the two vets, the two owners and the cat, they found that the large animal vet had a different strain, so it was an unrelated infection. However, the strains from the cat’s vet, cat and the two owners were identical. Further, that strain was different from strains from people in that province (remember…the owners came from 900 km away).
This was the perfect storm that allowed for identifying likely pet-human transmission…exposure from an animal outside the household, a situation where the strain involved wasn’t common (or even present) in the background transmission in the area, timely testing of people and the animal, and an ability to sequence all the samples.
The most surprising aspect of this report for me is that they had the right conditions to find zoonotic transmission, not that it occurred. I’ve been pretty confident it was possible, which is why we’ve done animal surveillance and spent a lot of time developing and communicating practical but proactive guidance to vets to reduce the risk.
Cat owners shouldn’t have much to worry about. Odds of a cat bringing SARS-CoV-2 into the household are really low. However, if it gets in with a person and the cat gets infected (which can occur ~50% of the time), we have to think about the implications. If a household isn’t doing anything to separate infected and uninfected people, cats probably don’t matter much since human-human transmission is more likely. However, if households are separating those groups, include the cat. If I have COVID and move to the basement to stay away from everyone, I should keep my cat away from me too (or keep it with me and away from everyone else). It’s also a reminder that we should continue to query COVID exposure status of veterinary patients, and ideally postpone elective visits for cats from households with COVID. Emergencies are a different story and we can take precautions to reduce the risk, but it’s preferable to bump an elective appointment.
All this relates to cats…what about dogs?
The risk from dogs is unclear and is probably very low. We don’t have evidence of dog-dog transmission and viral loads in infected dogs are typically low. I don’t think we can say there’s zero risk, but the risk is likely much lower compared to cats.