A rash of COVID deaths of farmed mink in Wisconsin last fall raised alarms that the operations could spread the virus to wild animals or even create dangerous new variants, similar to a variant that led the Danish government to order all mink in the country killed last year to prevent a major outbreak.

Veterinarians in Wisconsin and Minnesota say they don't see cause for alarm, but also acknowledge that there are still plenty of unknowns.

"It does concern me anytime you have a disease that can go from people to animals and then back to people again," said veterinarian Dr. Gail R. Hansen, a consulting vet with the Humane Society and the former Kansas state epidemiologist.

But she added that she's not "running around with her hair on fire about it."

"We have to be pretty humble about what we don't know," Hansen said.

The Wisconsin farms, many of them about 150 miles east of the Twin Cities in Taylor County, have largely rid themselves of the virus in recent weeks, and a vaccine trial that concluded last week could bring promising results soon, said Dr. Hugh Hildebrandt, a veterinarian from Medford, Wis., who specializes in mink.

"It looks like in fairly short order we will likely have a vaccine for the mink industry," he said.

The U.S. mink fur industry's brush with COVID hasn't made much of a splash amid the larger pandemic, even though the consequences are no less threatening than what people have faced over the past year. There have been foiled efforts to stave off infection, sudden waves of illness sweeping through a confined population and even mass casualties. The U.S. mink fur industry had some 245 farms producing 3 million pelts across 22 states as of 2018, according to the Fur Commission, a trade group.

Hildebrandt said the outbreaks that killed 5,500 mink on two Wisconsin ranches lasted up to 10 days, and likely began when a person with the virus infected an animal. Some 16 outbreaks have been reported at mink farms nationwide, with 12 of those in Utah, according to a list compiled by Wisconsin Watch, a nonprofit news outlet.

A spokesman for the Humane Society, which has long opposed fur farming on ethical grounds, said mink farms in Minnesota, Wisconsin, Michigan, Utah and Oregon should institute mass COVID-19 testing.

"We are only testing when there is an increase in mortality rates. … We're not doing enough," said PJ Smith, the Humane Society's director of fashion policy.

Smith pointed to a study published last month in Science, the journal of the American Association for the Advancement of Science, that found evidence of animal-to-human transmission of COVID-19 near mink farms in Europe. The fear is that the virus could mutate within the animal population before jumping back to people, possibly in a form that renders current vaccines ineffective or makes it harder to track.

While an alarming prospect, the Science article said more study is necessary to understand whether there's a risk that the mustelid family, including mink, otter, ferrets, badgers, weasels and other species, could become a reservoir for COVID-19.

Mink are not considered livestock in Minnesota and are not closely regulated by any single state agency. The Board of Animal Health and the state Health and Natural Resources departments would all respond if there was concern that a mink farm in Minnesota was infected with COVID-19 and could potentially see animal-to-human transmission, according to a spokesperson.

State officials with the Board of Animal Health sent information last year to the state's four licensed mink farms, urging farmers to strengthen their biosecurity precautions and to use personal protective gear and take other pandemic safety steps to prevent passing the disease to their animals.

A veterinarian who finds a positive test result on a mink farm must report it to state officials. The state has received no such reports.

In Denmark, one of the world's largest pelt producers, officials have taken a far more heavy-handed approach. Concerns that mink could become the source of a significant outbreak led the government last fall to order all mink killed, whether or not they were infected, at some 1,100 farms. Outbreaks in other countries, including Spain and the Netherlands, were also treated with mass culls.

Dutch authorities also accelerated a plan to phase out fur farming, ending the industry this year.

At Hough Fur Co. near Fargo, one of the few mink farms left in Minnesota, owner Dustin Hough said his family came down with mild or asymptomatic cases of COVID a year ago, with no known effect on their mink. He's since monitored his stock for signs of illness but doesn't consider the virus his only worry.

"I'm just as worried about distemper," said Hough. He said state officials called him to talk about what happened in Denmark but he wasn't asked to depopulate his herd.

Hough defended his care of mink, saying the success of his operation depends on keeping the animals healthy.

"If you're not on top of everything with mink, you're going to lose mink," he said.

Dr. John Howe, former president of the American Veterinary Medical Association, said he doesn't see mink farms as a problem for people right now, and he hasn't seen credible reports of people catching the virus from mink in the United States.

DNR wildlife biologist John Erb said that while a zoonotic virus is a concern, the idea that mink could incubate a new variant and pass it to people is "more one of those hypotheticals" than anything else.

Minnesota state veterinarian Dr. Beth S. Thompson said it's worth monitoring the latest research but for now she thinks the focus should be on human illness.

"We're still at the point in the pandemic where we need to focus on the people," she said.

Matt McKinney • 612-673-7329