4 Michigan residents were probably the first American mink-to-human COVID-infecting case
Kristen Jordan Shamus, Detroit Free Press and Betsy Ladyzhets and Derek Kravitz, Documenting COVID-19 project, Columbia University’s Brown Institute for Media Innovation and MuckRock
Four Michiganders – a conservator, his wife and two mink farm employees – were infected with a unique coronavirus strain associated with mink, prompting Michigan health officials and the CDC to conclude that they probably had the first known U.S. cases of so-called animal two-human virus “spillover”.
Michigan’s four mink-linked COVID-19 cases – the only known animal-to-human cases in the United States to date – have infected more people than previously known.
The Detroit Free Press and the Documenting COVID-19 Project first reported on the mink cases in April 2021after discovering details about them in Freedom of Information Act requests and National Geographic confirmed last month that four cases with the same genetic mutations had been linked.
All four people recovered fully.
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There have been other animal-to-human COVID-19 cases documented in Canada with white-tailed deer and a hamster in Japan. While Michigan’s cases are the only known animal-related COVID-19 cases in the United States, there may be other cases that have been unreported as the country does not actively test for such outbreaks.
The investigation into Michigan’s mink outbreak began in October 2020. Samples from two mink farm workers who tested positive for COVID-19 had virus mutations that were also present in samples from mink on the farm.
At the time, the state Department of Agriculture issued a statement saying, “There is currently no evidence that animals, including mink, play a significant role in the spread of the virus to humans in Michigan.”
Nearly two months later, a conservator in Eaton County also tested positive and showed the same two mutations in the genetic sequence of his sample. He had no known connections to the mink farm, suggesting he was probably infected in the community. A fourth person was also confirmed to have the same mutations in February 2021.
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“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,” said Lynn Sutfin, a spokeswoman for the Michigan Department. of Health and Human Services.
“Since close contact with mink would be necessary for the virus to spread from mink to humans, the risk to people outside farms, including those living in nearby areas, is likely to be very low.”
The animals on the farm subsequently tested negative for virus twice and were released from quarantine.
It is unclear how many mink farms operate in Michigan, or the number of animals raised on those farms. The Michigan Department of Agriculture and Rural Development does not register or license mink farms, Department spokeswoman Jennifer Holton said.
However, the U.S. Department of Agriculture has some data from one self-reported census last taken in 2017, suggesting that Michigan was home to 12 mink farms with as many as 22,000 animals that year.
There is still no active monitoring or testing required on mink farms, according to the CDC. It is not a reportable disease in animals in the United States
On the contrary, officials at the CDC and the U.S. Department of Agriculture are working with state health ministries to decide if and when animals should be tested for the virus.
Animal testing is recommended for livestock, including mink farms, if the animals show signs of having coronavirus or if their exposure to humans who have had the virus is unknown, the CDC said in a statement.
The State Ministry of Agriculture makes decisions on when animals and animal by-products should be quarantined on affected mink farms.
In this way, the United States is unique from countries in Europe that actively monitor mink and mink farm workers for COVID-19, said Jim Keen, a veterinary epidemiologist at the Center for a Humane Economy. Keen has previously worked at the USDA and specializes in infectious diseases among livestock, with a recent focus on COVID-19 in mink.
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“The United States is a true outlier” in its strategy to deal with mink contagion, Keen said. Federal and government agencies has approved a COVID-19 vaccine for mink and encourages farmers to use it. But the vaccine does not prevent COVID-19 infection or transmission – in the same way as human vaccines – so surveillance is still needed, Keen said.
“The CDC constantly says, ‘Mink transmission to humans is very rare,'” Keen said. “But we are not testing. … It is self-reported by mink producers, and mink producers do not want to report. ”
There have been at least 18 known COVID-19 outbreaks among mink on mink farms in the US, out of an estimated 60 total farms in the country – 12 in Utah, three in Wisconsin, one in Oregon, one in Michigan and one in an unidentified location, according to US Department of Agriculture. The true number of outbreaks could be much higher if proper tests were performed, Keen said.
Virus mutations identified in the mink on the Michigan farm have previously been seen in mink from farms in the Netherlands and Denmark, as well as in people associated with mink farms worldwide.
Mink are able to get COVID-19, just like humans and many other mammals, because their cells have a protein called ACE2 that makes it easy for the virus to enter and replicate. However, farmed mink are particularly susceptible to the virus because they live close to each other and have a weaker immune system from crossbreeding, according to the CDC.
Federal health officials say anyone with COVID-19 should be isolated from other people and animals, including pets. They should also stay away from farms where animals are raised.
This contagion on the mink farm also shows the importance of continued COVID-19 monitoring in wildlife. Researchers see the spread of the virus in animals as a potential source of new variants that may be more contagious or avoid protection against vaccines.
In a statement last month, the World Health Organization suggested that people working closely with wildlife should receive training to reduce the risk of transmitting disease. National health organizations like the CDC are responsible for monitoring wildlife that may become infected and publicly sharing all information about animal cases, including genetic sequence data, the WHO said.
Currently, the United States does not have a comprehensive system for monitoring COVID-19 in animals or potential transmission between animals and humans, according to a report by more than 50 COVID-19 experts, including former federal government officials.
“The CDC should change its strategy,” Keen said. “At least go out and test all 60 mink farms, do genetic sequencing and see what happens.”
Contact Kristen Shamus: [email protected] Follow her on Twitter @kristenshamus.