The infections appear to be caused by a mutated version of the virus that’s made the jump to humans from the diminutive, furry mink. Denmark is the world’s largest mink producer, with exports typically headed for the fashion industry in Asia.

To limit the spread, local Danish officials on Thursday placed the impacted parts of the country under tighter COVID-19 restrictions, Reuters reported. That’s after the national government warned on Wednesday that the mutated mink-borne version could not only be a health risk to humans, but that these infections could undermine larger, global efforts to create an effective vaccine.

In addition to imposing more stringent lockdown measures in the region, the government also said it will cull the country’s entire population of about 16 million minks.

The World Health Organization said Thursday that it is aware of reports in Denmark of humans being infected with COVID-19 by mink—with some genetic changes to the virus—and that it is in touch with authorities about the matter.

Such a mutation could have “devastating consequences worldwide,” Danish Prime Minister Mette Frederiksen said Wednesday.

A Danish government report has linked a mutated COVID-19 strain to 12 cases in the country’s north, and the health minister said more than half of the over 700 cases in the region had been linked to mink, which are farmed for their soft pelts. Culling on some farms has already begun as COVID-19 has spread throughout farms in the region for months.

But James Wood, head of the department of veterinary medicine at the University of Cambridge, urged caution.

“The true implication of the changes in the spike protein have not yet been evaluated by the international scientific community and are thus unclear,” he said in a statement. “It is too early to say that the change will cause either vaccines or immunity to fail.”

Infections of mink with COVID-19 have been tracked in western Europe since at least April, and Dutch mink farms have also reported COVID-19 cases and instituted large culls. As early as May, an investigation by the Dutch government warned that mink may be already transmitting the virus to humans, forcing it to create strict reporting systems among the country’s farms to track outbreaks. The government also warned of the risk of virus mutations at the time.

In late October, the Danish newspaper Information reported that a risk assessment by the Danish Veterinary and Food Administration, the state Serum Institute, and the University of Copenhagen had warned the government of the mutation in the virus among mink. The assessment also concluded that efforts to prevent the infection of humans by mink hadn’t worked or hadn’t been properly implemented.

Besides the risk of mutation, the cases raise serious questions about the future of the mink industry. In the Netherlands, the sector is required to be phased out completely by 2024 on animal welfare grounds, while there is also political support in Denmark for such a ban.

It’s not the only virus-related animal cull at the moment. Authorities in Germany, the U.K., and the Netherlands are also racing to contain outbreaks of the H5N8 bird flu at several poultry farms. Though there is little transmission to humans, the culls will put a further economic burden on the agriculture sectors as economic crises mount.