Around 11 a.m. on a Friday in October, Poulsen got the call he’d been expecting for months. Mink in Medford were sick, and it looked a lot like COVID-19.
Medford, a city of just more than 4,000 people in north-central Wisconsin, used to call itself the mink capital of the world. There, a person can live in the neighborhood of “Mink Capital Terrace” or on a road called “Mink Drive.” A generation ago, a Medford girl could have aspired to be crowned Mink Princess U.S.A. at the annual Medford Mink Festival.
Though the United States mink industry has shrunk along with Americans’ waning appetites for fur coats and the festival is no more, Wisconsin is still the country’s biggest producer of mink pelts. And Medford is still a mink town; there are 12 mink ranches in the area, within five miles of one another—and the coronavirus has now reached two of them.
Once the coronavirus finds mink, it works fast. When Poulsen picked up the phone, the veterinarian for the Medford-area mink ranches told him that several hundred mink had already died. Plus, some people on the ranch had COVID-like symptoms. “I think we need them tested,” the vet said. By 11:30 a.m., Poulsen was driving a van 250 miles upstate; by the time he arrived at the ranch, at 3:30 p.m., several hundred more mink had died.
Mink are extremely vulnerable to respiratory disease. Like people, they get seasonal respiratory issues. They’re also prone to pneumonia. Respiratory viruses replicate so readily in minks and their mustelid relatives (ferrets, most notably) that the animals are often used to study human illnesses.
So mink can get the coronavirus, and they can get it from people; as cases in humans rose precipitously in Wisconsin this fall, Poulsen and his staff figured it was just a matter of time before someone on a mink farm sneezed it into the mink population. So did the local veterinarians. “We were just waiting,” says Dr. John Easley, a mink specialist who serves as a veterinarian for mink ranches in southern Wisconsin. Both mink and human cells have specific receptors that allow the virus to attach to them, which made mink a greater concern than other farmed animals, including Wisconsin’s immense dairy-cow population, he says. “Cows don’t allow the virus to enter their cells quite as easy. They do get infected, but the virus just doesn’t replicate very well in their system.”
Farmed mink have proved to provide absolutely excellent conditions for the virus to be fruitful and multiply. In addition to all of the ways mustelid physiology makes them similarly predisposed to the malady as humans, mink on farms are housed closely together. Social distancing is out of the question, and transmission is all but guaranteed. As of December 3, a total of 644 people associated with mink farms had contracted COVID-19 since June, along with another 338 people who work in mink pelting, according to a World Health Organization report that came out before the news of Canada’s outbreak, where an additional eight people on a mink farm have been sickened. In mid-November, a virologist at the Danish health authority told Nature that COVID-19 mutations believed to have originated in mink had shown up about 300 times in people in Denmark.