The first behind-the-scenes look at the US Centers for Disease Control and Prevention’s (CDC) investigation into a probable COVID-19 animal-to-human spillover event in Michigan in late 2020 is revealed in a cache of official documents. The records, as well as the CDC’s responses to them, show that the CDC had been aware for at least three months that mink on a fur farm may have infected humans before quietly updating its website in March 2021.
The delay in publicly disclosing this suspected spillover event, according to coronavirus researchers, may have hampered their ability to effectively monitor the spread of the SARS-CoV-2 virus. Experts warn us that this could spread to another species, mutate, and then return to humans as a more dangerous or transmissible variant.
“This should keep reminding us that disclosure is crucial, and the faster you know things, the faster you can act,” says Scott Weese, head of the University of Guelph’s Centre for Public Health and Zoonoses. He believes that earlier knowledge of the probable spillover cases could have aided other countries in improving their pandemic surveillance and response.
Emails between the CDC and Michigan public health officials, which formally requested the agency’s help on October 8, 2020, after the state affirmed that mink on a fur farm were exposed to the virus, are among the thousands of pages of documents released under the Freedom of Information Act and largely redacted. According to emails, the CDC deployed four veterinary epidemiologists to Michigan within days, where they obtained viral samples from mink on the farm and people in the region as part of a study into how the virus spread.
Finally, genomic analysis of virus samples from two mink farm workers and two people with no known link to mink revealed that they were both infected with a distinct coronavirus variant previously found in mink and in human-to-mink transmission in Europe.
In an email to National Geographic, CDC spokesman Nick Spinelli said that all “important material” was finally put on the CDC’s website, and that the news wasn’t “surprising or unexpected” because comparable instances had been documented in Europe.
The genomes of those four virus samples were made public between November 4, 2020, and February 23, 2021, according to Spinelli, because they were uploaded to GISAID, a public worldwide coronavirus database. Users must, however, create an account, learn how to browse the site, and comprehend genomic sequence mapping in order to access the database.
There is no additional danger to CDCs delayed announcement
According to Spinelli, there’s little evidence that mink had a substantial role in the virus’s propagation among humans or that the mink-associated variety circulated in the Michigan community for a long time. Angela Rasmussen, a virologist at the University of Saskatchewan in Canada suggests that Michiganders did not need to take any further precautions at the time because safety advice, such as wearing masks and social separation, would have stayed the same.
According to the CDC, these four instances in Michigan are the only suspected mink-to-human coronavirus infections in the United States. A white-tailed deer in Canada and a hamster in Hong Kong are the only other animals thought to have transmitted the virus to people.
The CDC, according to Spinelli, cannot state with certainty that mink transmitted the virus to people. “It’s impossible to know for sure whether the mutations arose from mink on the farm or were already circulating in the community because there are few genetic sequences accessible from the populations around the farm,” he explains.
Little is known about the four persons in Michigan. But this is a fact that two of them, according to the CDC, reside in the same house—got the mink-associated variant. They had no link to the mink farm, this shows the variant travelled beyond the farm and into the community for months.
According to Spinelli, all four humans have recovered completely. The surviving mink on the affected farm have tested negative for the virus.
The United States House of Representatives enacted legislation banning mink farming nationally in February 2022. It has yet to clear the Senate, but animal welfare organisations have backed it, claiming that the industry is both dangerous to humans and inhumane.
Due to concerns about coronavirus spread, Denmark and the Netherlands, both significant mink breeders, will slaughter millions of farmed mink in 2020. In March, Ireland approved legislation prohibiting fur farming.