We know cats are susceptible to SARS-CoV-2, and it appears that human-to-cat transmission may be pretty common in households where people have COVID-19. In the big picture, that’s probably not a huge issue, since most cats that get infected show no signs or develop only mild disease, and most infected cats have limited opportunity to spread the virus outside their own household. However, we still need to understand more about infection in cats and other species, to make sure we understand the true risks (if any) and how to mitigate them.

Expanding on their earlier work, a research group from Kansas State University looked at susceptibility of experimentally infected cats to re-infection with SARS-CoV-2.  The study has been posted as a pre-print on bioRxiv (Gaudreault et al. 2020).

• When they re-exposed cats to the virus 21 days after their initial infection, the cats got infected again, but infection was less common and mild.  Also, while infected cats could pass the virus to other cats during their initial infection,  the re-infected cats were unable to infect others.
• So, while the cats were susceptibile to re-infection, the infection was mild and they didn’t seem to pose a transmission risk on the second go-around.
• Therefore, natural infection is expected to provide some, but incomplete, immunity in cats (which is not too surprising, given what we know about infection in people).

An important aspect of this study to keep in mind is that the cats were re-infected quite soon after the first infection.  The study showed some protective effect after 21 days, but we don’t know how long this incomplete immunity may persist.  Duration of immunity after infection (and after vaccination) is a big question is humans as well. We’re hoping that natural infection or vaccination provide reasonably long-term immunity, but that may not always be the case. That will have a major impact on how this pandemic progresses, and how we approach vaccination in the long-term.

Overall, this study provides some useful information, but it doesn’t change anything we do at the moment. The key messages remains the same:

• If you have COVID-19 or have been exposed to the virus, limit contact with animals (just like you would with people).
• Cats are people too, at least from a disease control standpoint. If your household is isolating, that should include all the non-human critters. It makes no sense for me to lock down all the people in my house but still let my pets have contact with other people and animals.
• SARS-CoV-2 is (now) a human virus, but it still has an affinity for certain other species. Our goal should be to keep this a human virus and try to prevent it from infecting other animals.
• If you’ve had COVID-19 once, hopefully you won’t get it again – but you might. Previous infection isn’t an excuse to change your behaviour or stop using basic prevenative measures around other people or animals.