When you have people with COVID-19 and they have contact with animals, there’s some risk of infecting the animals. The risk varies by animal species, but this virus seems to have the ability to infect a few different species beyond our own.
SARS-CoV-2 has been identified in mink on two farms in the Netherlands. There were sick employees at both farms, so it’s assumed the workers infected the mink. Whether it was all worker-to-mink transmission or whether there was any subsequent mink-to-mink transmission is presumably being investigated (difficult as that may be to determine).
The scope of the problem isn’t clear from the reports I’ve read. It’s been stated that between the two farms there are over 20 000 mink, and the ones that were sick had intestinal and respiratory disease. How many were sick and how many were tested isn’t yet clear. Infection on a farm with that many animals is certainly a concern; while mink are generally not housed in cages together, they are usually close enough that aerosol or droplet transmission between animals would still be quite possible.
Roads around the farms are being closed and people are being told to stay at least 400 metres away, while the investigation continues. Issues such as potential virus transmission on dust particles (since other bacteria and viruses can sometimes be found downwind of affected farms) and what to do with the mink manure are being considered. Manure handling may be a particular concern since shedding in feces is likely, and 20 000 mink can produce a lot of feces.
Cats on the farms are also being investigated. It’s important to know if the cats are also infected as an indicator of whether the virus can spread in animal groups (although the cats could theoretically have been infected by the same workers). As I’ve said repeatedly, COVID-19 is almost exclusively a human problem, but a small animal component could still be a concern, if animals can re-infect people or act as reservoirs. We’re addressing the animal component in large part to try to keep this as an exclusively human problem.
Infection of mink isn’t surprising because they’re related to ferrets, and we know that ferrets are susceptible based on experimental work that’s already been reported. This also shows again how “predicted” susceptibility can be dodgy, as a recent pre-print article on the topic listed mink and ferrets in the “very low risk” category – clearly they are not. We need more study of animals and this virus, as well as continued efforts to keep sick people away from animals, and to keep exposed animals away from other animals and people.