Derek Kravitz and Bianca Fortis, Brown Institute for Media Innovation; Miriam Marini, Detroit Free Press
A Michigan taxidermist who got infected with COVID-19 is at the center of a medical mystery that borders on the bizarre: Did he get infected by a mink — the animal susceptible to the virus and farmed for its fur — or a human?
Medical experts have, so far, been unable to answer that question, though records obtained in a joint Centers for Disease Control and Prevention, state and county health investigation show a potential link to a nearby mink farm.
In early February, a taxidermist living in Eaton County, became infected with COVID-19. A sample from his positive test result was sent to the state lab to be genetically sequenced — and came back as connected to a mutation of the virus found in infected mink, whose fur is used for coats and clothing.
And yet the taxidermist had no known exposure to a Michigan mink farm where two employees had become infected with a mink-associated strain months earlier, suggesting he was infected in the community, according to the CDC.
“Because there are few genetic sequences available from the communities around the farm, it is impossible to know for sure whether the mutations came from mink on the farm or were already circulating in the community,” the CDC said in a statement to the Documenting COVID-19 project at Columbia University’s Brown Institute for Media Innovation and the Free Press.
Michigan, Oregon, Utah, Wisconsin and other states with mink farms have dealt with COVID-19 outbreaks — and an unknown number of farmworkers in Oregon and Utah who had direct contact with the mink have become infected — but the CDC has cautioned repeatedly that mink-to-human transmission is exceedingly rare. In all of the cases, it’s ultimately unclear whether mink infected people or vice versa. Mink are particularly susceptible to COVID-19 and entire populations of the animal have been killed across Europe to stamp out the virus’s spread.
And, with the limited data available, it’s difficult to pinpoint whether the Eaton County virus mutation is unique to mink and represents the first documented cases of mink-to-human community transmission in the United States, according to epidemiologists, virologists and the CDC.
“Individuals who are linked by transmission are more likely to have similar, or even identical sequences,” said Dr. Adam Lauring, a University of Michigan virologist whose lab performs genetic sequencing for the state. “But it is also possible for individuals who are unlinked to have identical sequences.”
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The details of the case are sparse: The taxidermist and his wife live in Eaton County; they may own a small farm, and a detailed questionnaire revealed the taxidermist handled deer and backyard chickens but was exposed to no other animals, according to internal health department emails obtained through the state’s Freedom of Information Act.
Because of the potential involvement of an infected mink, the CDC took a “significant interest” in the case, emails show.
In October, the Michigan Department of Agriculture and Rural Development confirmed the first cases of COVID-19 of mink at a farm in the state, which was not identified. The farm’s owner had contacted state officials after several mink became sick and died from the virus.
At the end of November, the CDC and Michigan Department of Health and Human Services sequenced genetic samples from both infected mink and mink farm employees. They found that two farm employees who tested positive for COVID-19 had two virus mutations also found in mink on the farm.
In early February, the linked COVID-19 case involving the Eaton taxidermist was confirmed through genetic testing. The Barry-Eaton District Health Department, which includes the Eaton County area, conducted an enhanced case investigation with questions from the CDC. But it was “unable to find a link to how this individual would have been exposed to that mink COVID,” said Sarah Surna, a community health promotion specialist and spokesperson for the Barry-Eaton Health Department.
The virus sequencing of the Eaton taxidermist — collected almost two months after the original mink became sick — also showed the same two mutations.
MDHHS confirmed the CDC’s account of the mutations, identifying them as F486L and N501T. Those two mutations have been identified by researchers as the dominant mink COVID-19 strains in the United States, according to a preprint study published last month by two Canadian researchers, and may have evolved in humans before being transmitted to minks, A review of the case ID in GISAID, a global database of coronavirus genomes, shows the original mink-associated strain was collected in November and analyzed by MDHHS in December.
COVID-19 has been found in both domestic dogs and cats and wild animals, including lions, tigers and snow leopards. Canada has reported farmed mink outbreaks. To combat the virus, the Netherlands culled its entire population of 4 million mink and permanently closed down its mink industry.
And there have been documented cases of mink-associated infection among farm workers in Oregon and Utah. In Denmark, a mink outbreak led to more than 200 human cases, including 12 with a unique variant that Danish officials worried could make vaccines less effective.
But the U.S. mink industry is a fraction of the size of its European counterparts, with roughly 275 farms spread across 23 states.
The CDC notes that to definitively prove mink-to-human transmission of the virus resulting in community spread would require widespread genomic surveillance in mink, mink farm workers and the larger community, along with epidemiologic investigations to determine how the cases are connected to one another.
Mohar Chatterjee of the Brown Institute for Media Innovation contributed to this report.