Prime Minister Mette Frederiksen said the mutated virus posed a “risk to the effectiveness” of a future vaccine against Covid-19.

Denmark is the largest producer of mink fur in the world.

Police said the animals should be slaughtered as soon as possible.

Cases of infection with the new coronavirus have been detected for several months on mink farms in the northern region of Jutland (Denmark), but also in other parts of Europe. But they are spreading rapidly in Denmark, where five cases of infection with the new strain have been discovered on mink farms. Twelve people were contaminated, authorities said.

Frederiksen described the situation as “very, very serious”. She cited the results of a government report that the mutant version weakens the body’s ability to form antibodies, making it possible for vaccines now under development to be ineffective.

“We have a great responsibility to our people, but with the discovery, we have a greater responsibility to and to the rest of the world,” she told a news conference.

Minks from more than a thousand farms will be slaughtered.

In July, Spain slaughtered 100,000 minks after cases were detected on a farm in the Aragon region. Tens of thousands of specimens were also slaughtered in the Netherlands, where outbreaks were found on several farms.

Studies are underway to find out how and why minks contracted and spread the coronavirus.