COVID-19: Have US Public Health Officials Tried to Contain an Animal-Human Virus Outbreak?

US government documents obtained by National Geography provide a first behind-the-scenes look at the US Centers for Disease Control and Prevention (CDC) investigation into a suspected animal-to-human case of COVID-19 in Michigan in late 2020. Documents and statements made by the agency after its disclosure, indicate that the CDC already knew that the cultured mink had potentially infected humans for at least three months before silently releasing the update from its website in March 2021.

According to researchers specializing in the coronavirus issue, the delay in disclosing this alleged spillover case to the public may have hampered its ability to effectively monitor the spread of the SARS-CoV-2 virus, which experts say can affect another species, to mutate. and then return to humans as a more dangerous or more contagious variant.

“This situation should remind us again that transparency is important and that the sooner we know, the sooner we can act,” said Scott Weese, director of the Center for Public Health and Zoonoses at the University of Guelph in Canada. Had information on suspected cases of spillover been released earlier, he said, it could have helped other countries better monitor and respond to the pandemic.

These thousands of pages of documents, released under the Freedom of Information Act and many of which have been censored, contain emails exchanged between the CDC and Michigan State public health officials, who officially asked the organization for help on Feb. October 2020, after confirming that mink from a local farm had been contaminated. The emails show that, in just a few days, the CDC sent four veterinary epidemiologists to Michigan, who collected samples from the mink at the farm, but also from a few people who lived nearby to study the spread of the virus.

Ultimately, genome analysis of virus samples from two farm workers and two people with no known connection to mink showed that they had been infected with a unique coronavirus variant previously identified in these animals and in cases of mink-to-human transmission. identified in Europe.

The CDC defended its decision not to make a formal public announcement about the findings, which received minimal US media coverage beyond a newspaper article. Detroit free press in April 2021, a month after the CDC updated its website. One of his spokespersons, Nick Spinelli, said National Geography emailed that all “relevant information” was finally posted on the CDC website and that similar cases had been identified in Europe, the news was not “surprising or unexpected”.

Spinelli added that the genomes of these four virus samples were known to the public because they were uploaded to GISAID, a global public database specializing in viruses like COVID-19, between November 4, 2020 and November 4, 2020. February 2021. The database, however, requires users to register for an account, know how to use the site, and understand genomic sequence mapping.

Throughout the CDC’s investigation, its spokespersons have repeatedly said National Geography that there was “no evidence of mink-to-human spread in the United States,” including in an email sent in early January 2021. Internal email exchanges and statements by Spinelli indicate, however, that these claims were False: As early as November 4, 2020, the viral genomes of the two Michigan ranchers were found to have the mink-associated mutations, and by late December, the genome of the third case had also been sequenced and uploaded to GISAID.


According to Spinelli, there is no evidence that mink play a significant role in the spread of the virus between humans, or that mink-associated variants have circulated long-term in Michigan communities. In addition, residents of the state did not need to take additional precautions at that time, according to Angela Rasmussen, a virologist at the University of Saskatchewan in Canada, because health protection recommendations such as mask use and social distancing would not have changed.

These four Michigan cases are the only suspected human spills in the United States, according to the CDC. Aside from mink, the only other animals that have transmitted the virus to humans are a white-tailed deer in Canada and a hamster in Hong Kong.

A growing number of other species, including lions, tigers, gorillas, hyenas, dogs and cats, are vulnerable to COVID-19, but are unlikely to play a significant role in the spread of the virus between humans, according to claims by the CDC. and other experts.


The CDC cannot say for sure that the mink transmitted the virus to humans, according to Spinelli. “Because we have few genetic sequences from communities that live close to the farm, it’s impossible for us to know for sure if the mutations came from the mink on the farm or if they were already circulating in the community,” he says.

Other experts say, however, that while the mutations occur randomly, the variant is unlikely to have another origin. “The more mutations there are, the less likely it is to happen by chance,” says Weese.

According to Rasmussen, the lack of definitive answers in investigations such as this one highlights the need for more investment in sequencing the virus genome, both in humans and in infected animals. Epidemiologists could thus better fill in the gaps in their mapping and understand how the virus is transmitted from one person or animal to another.

We know little about the four Michigan people, but the fact that two of them (who live in the same house, according to the CDC) contracted the mink-associated variant when they had no link to the farm suggests that the variant has spread beyond the farm. in the community, and continued to circulate for months.

The four people made a full recovery, Spinelli said, and the surviving mink from the affected farm later tested negative for the virus.

The emails also show that Illinois was initially reluctant to allow mink pelts from Michigan livestock into its territory, but ended up accepting more than 17,000 in November 2021. The exchanges also show that the CDC and health officials Public authorities in several states were concerned about the mental health of mink farmers, who have witnessed widespread outbreaks of coronavirus in their animals and are receiving increasing calls to end the mink fur industry.

In February 2022, the United States House of Representatives passed legislation banning mink breeding across the country. This law has yet to pass the Senate, but it has strong support from animal welfare groups who accuse the industry of being inhumane and too risky for humans.

Ireland passed a law in March banning the breeding of furry animals. In 2020, Denmark and the Netherlands, two major mink producers, culled millions of farmed mink amid fears of repercussions from COVID-19. The Netherlands voted to immediately halt mink breeding, hastening the already-planned end of its mink fur industry.


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