Denmark is taking aggressive action to stop the spread of coronavirus outbreaks on mink farms that have now seemingly jumped back into humans.
On Wednesday, Danish Prime Minister Mette Frederiksen announced that farm workers have contracted infections with strains of the virus that contain a mutation first found in infected minks—a mutation that public health officials fear could possibly affect our immune response to the virus. The government plans to kill all of its farmed mink population, estimated to be as high as 17 million total. But it’s still unclear whether this mutation may truly be important.
Minks and other weasels have turned out to be one of the unexpected casualties of the covid-19 pandemic, as they’ve proven vulnerable to catching the virus from infected people and then easily spreading it to each other. And unlike other animals known to have contracted human-spread infections, such as cats and dogs, the virus seems to be especially deadly for them. In early October, health officials in Utah and Wisconsin reported that recent outbreaks had led to over 10,000 minks dying.
The first known outbreaks of covid-19 among minks occurred in Europe over the summer. These initial outbreaks prompted countries such as the Netherlands to preemptively kill off more than a million minks to stop transmission. But it seems that the virus has continued to spread on Denmark’s mink farms, and it’s possible that some of these circulating strains have mutated to become meaningfully different from those infecting people and are starting to spread back to us.
In a press conference Wednesday, Frederiksen said that more than 300 people in Northern Denmark (roughly half of all known active cases in the region) had recently contracted strains of the virus tied to mink farms. Several of the cases found in both people and minks appeared to contain a shared mutation. And when health officials studied the strains of virus isolated from these cases closer, they found evidence that these mutated strains may be not as sensitive to our antibodies as expected. So far, five minks and 12 people in the country are known to have contracted this particular variant of the virus.
“The mutated virus in mink may pose a risk to the effectiveness of a future vaccine,” Frederiksen said, according to Reuters.
Some caution is warranted here. Without more publicly available data on the mutation, outside scientists can’t yet confirm what Denmark’s scientists have claimed to find. It’s possible this mutation may not be relevant at all, even if it has spread from minks to humans. Mutations in a virus happen all the time, and it often takes multiple lines of research to know whether any one mutation is changing the relationship between a virus and its host. Perhaps most crucial is that, even if a mutation is bad news for us, that doesn’t necessarily mean that it will spread widely among strains circulating in the population, for many complicated reasons.
Still, scientists do generally worry about this kind of scenario happening, where a virus that spreads between different kinds of hosts can pick up mutations that give it a new advantage when infecting people. Indeed, it’s thought that the original strains of the virus that led to the covid-19 pandemic came from animal-to-human transmission in the first place, possibly spreading to us from bats. And it’s possible, though not confirmed, that the virus may have already mutated to become more infectious in people early on in the pandemic.
But though the findings on this latest mutation may be valid, Emma Hodcroft, a researcher at the University of Bern in Switzerland who studies the genetics of the coronavirus, said she was disappointed in how Denmark decided to announce them.
“When something like this is announced with no additional information and no context, it’s impossible for scientists to weigh in with assessments and interpretation. However, headlines and quotes like those given spark a lot of worry in the public and also lead to a lot of media attention—when we have no data to work with,” she said. “I strongly believe everyone has a responsibility to report on SARS-CoV-2 research—especially things about mutations and vaccinations—responsibly.”
Among other caveats, Hodcroft noted that a weaker antibody response caused by a mutation in the coronavirus, even if genuine, may not necessarily impact a vaccine’s effectiveness. But without further data available, it’s too early to know much of anything.
Denmark is taking no chances. Officials now plan to cull the entire mink population—a heavy toll for the world’s largest mink fur producer. But it will take more time to know whether this decision will have prevented something worse from coming down the line.
This article has been updated with comments from Emma Hodcroft.