Last week, Denmark announced its intention to cull all farmed mink, some 17 million, out of fear that a mutated version of the coronavirus might diminish the effectiveness of potential vaccines. The decision has caused dismay in other countries and a debate among scientists about the validity of the concern.
Six countries — Denmark, the Netherlands, Spain, Sweden, Italy and the United States — have reported cases of farmed mink infected with SARS-CoV-2, the virus that causes Covid-19. Mink catch the virus from humans and pass it on to each other. Unlike dogs, cats and some other animals, which express only mild symptoms, if any, mink can sicken and die from an infection.
Here are answers to basic questions about mink and the coronavirus:
Can mink infect people with the coronavirus?
Yes. In Denmark, mink have contracted the virus and spread it to people. The same happened in the Netherlands this year.
Does the virus mutate in mink?
Yes. In more than 200 people, Danish authorities have documented several variants of the virus that contain mutations originating in mink. The virus also mutates in people.
Is the mutated virus more dangerous?
No. There is no evidence that any of the mutations that originated in mink make the coronavirus more transmissible in humans or make humans sicker.
Why did Denmark decide to kill all of its farmed mink?
Danish health authorities were concerned that one set of mutations in a variant of the virus called cluster 5, which had infected at least 12 people, could make a potential coronavirus vaccine less effective.
One of the mutations occurs on a part of the virus — the spike protein — that is targeted by many potential vaccines. In lab studies, cells with this variant of the virus were exposed to antibodies, which did not act as strongly as they had with other coronavirus variants.
But this was a very preliminary test. The reaction to antibodies in laboratory cells does not necessarily indicate that the mutated virus would be resistant to vaccines; it merely raises that possibility.
Will the mutations diminish the value of vaccines?
The World Health Organization and independent experts said there was no evidence so far that the cluster 5 variant would diminish the value of vaccines currently in development.
Did Denmark overreact?
Scientists say that there are reasons beyond this particular mutated virus for Denmark to act. Mink farms have been shown to be reservoirs for the coronavirus, and mink are capable of transmitting the virus to humans. They are the only animal known to do so.
This set of mutations may not be harmful to humans, but the virus will doubtless continue to mutate in mink as it does in people, and the crowded conditions of mink farms could put evolutionary pressures on the virus different from those in the human population. The virus could also jump from mink to other animals. These are all worrisome possibilities, particularly in the midst of a resurgence of the virus in the human population.