OPINION: Can livestock spread virus to people?

Is there any evidence that a coronavirus can jump from animals to people and vice-versa?

Proving that something does not happen is always a bigger challenge than proving that it does. I think that it is well accepted that the coronaviruses that caused MERS and SARS jumped from animals to people. The actual animal of origin for MERS seems to have stronger proof than SARS but still the evidence for the origin of SARS is good. COVID-19 is a little tougher. People suggest that it came from bats; a recent research paper proposes that pangolins may have been an intermediate host — but there is no definitive proof yet. It will likely turn into one of those situations where there is a ‘scientific consensus’ rather than definitive proof.

It’s more difficult to answer whether this coronavirus can move from people to animals partly because it is likely less important unless it is also eventually turns out those animals are a threat back to people. There were reports that some dogs had been suspected of carrying COVID-19 early on. The test that was used there finds dead virus just as well as living virus so it was an open question if the dog was actually an active carrier (the virus infected the dog) or a passive carrier (the virus got on the dog and was there long enough to be detected by the test).

There was a study published in March looking to see if COVID-19 would grow in dogs and cats and they concluded ‘no.’ I will say, however, that proving something does happen is much more easily accepted than trying to prove that something doesn’t happen.

There are new studies (and preliminary studies) coming in everyday now. Some show that cats and ferrets can become infected with COVID-19 and shed virus. That was true for cats and ferrets with other coronaviruses too.

The only other mammal that large numbers of people have close contact with might be horses. I have not seen any studies yet for horses being challenged with the COVID-19 virus to see what happens. COVID-19 might turn out to be carried by some other animals but I struggle to wonder if it really would matter on a population basis in Canada. This virus seems to spread well enough between people that we likely need to worry about the risk from other people way more than about the risk from other non-human animals, at least at this stage of the epidemic.