Revelations on spread at mink farms indicate CDC did not adequately disclose data, creating a weak link in global response

The reputation of the US Centers for Disease Control and Prevention has been called into question after the revelation that thousands of government documents suggest that it delayed releasing information about the first animal-to-human transmission of COVID-19 on a Michigan fur farm in 2020.

The documents obtained under the Freedom of Information Act, initially by National Geographic last month, include emails between Michigan public health officials and the CDC that appear to show evidence that the CDC did not update its website for three months with a public announcement after it first discovered at least two cases.

Critics say that the CDC should have revealed the information immediately as it was "dangerous" not to keep scientists informed as they carefully documented how the virus was mutating and could affect humans.

Jim Keen, director of Veterinary Sciences at The Center for a Humane Economy, an animal welfare organization in Bethesda, Maryland, told China Daily: "Well, it was potentially dangerous, (not to release information immediately) because again, at that time, there was no vaccine and the situation in mink was relatively new, it was known to be moving through the European nations at that same time.

"In some ways, I would even say it was unethical, because one of the principles of public health is to report outbreaks immediately," said Keen, a former employee of the United States Department of Agriculture, or USDA. "And I don't know why they didn't do that … you're not supposed to hide that health information, especially from the public health community. And… certainly not from the public."

Lynn Sutfin, a spokesperson for the Michigan Department of Health and Human Services, confirmed that Michigan officials invited four veterinary epidemiologists from the CDC to the fur farm in October 2020. They carried out tests to detect coronavirus in the mink and employees on the farm after the state reported an outbreak there.

Sutfin told China Daily: "As part of a One Health investigation into a Michigan mink farm with SARS-CoV-2 in people and mink in Michigan, specimens were collected and tested from mink farm employees and mink on the farm in October 2020."

Extraordinary discovery

By Nov 4, 2020, after sequencing (examining) the specimens, the CDC made an extraordinary discovery. The samples from the two mink farm employees showed that they had not only tested positive for COVID-19, but the virus mutations that were present in the samples also came from mink on the farm. It indicated that the first mink-to-human transfer of COVID-19 had occurred in the US.

Months later, a further two people, a taxidermist and his wife, who lived in the same house in Eaton County, Michigan－but were not employees of the mink farm－tested positive in December 2020 and February 2021 with the same genetic mutations as those seen in the mink farm employees.

Sutfin added: "The mink were initially found to be infected and the human case investigation occurred after the mink were found to be infected.

"CDC and Michigan Department of Health and Human Services Bureau of Laboratories sequenced viral genetic material from these specimens, which showed that two farm employees who tested positive for COVID-19 had sequences containing two virus mutations (F486L and N501T) that were also present in sequences from mink on the farm."

Shortly after the findings, the state's agriculture department said in a statement: "There is currently no evidence that animals, including mink, play a significant role in spreading the virus to humans in Michigan."

What the CDC did next raised questions among public health experts and veterinarians.

While the agency knew that the two Michigan farmworkers' virus genomes had the mink-associated mutations by Nov 4, 2020, it wasn't until March 2021 that it updated its website with the information.

The CDC did not respond to two separate requests from China Daily to clarify why this occurred. Until January 2021, the CDC told National Geographic that there was "no evidence of mink-to-human spread in the US".

Nick Spinelli, a CDC spokesman, denied to National Geographic that the CDC's findings were delayed or kept private. He said, instead, that the genomes of those four virus samples were uploaded to GISAID, a public global coronavirus database, between Nov 4, 2020, and Feb 23, 2021. By December, the third case's genome was uploaded to GISAID.

Yet, this database requires users to register for an account and unravel complex genome sequence mapping. Two public health experts confirmed to China Daily that they had been unable to access the database, despite both having decades of experience in their field, so the evidence remains unseen by much of the public.

A mink-to-human transmission of COVID-19 had never been officially recorded in the US, but, internationally, mink-to-human spread of COVID-19 had been reported and confirmed in the Netherlands and Denmark.

Public health experts believe that the information in GISAID on outbreaks containing the spike protein Y453F in Michigan and Wisconsin would have also likely remained hidden from public view if it were not for two Canadian researchers who had GISAID access and downloaded complex sequencing from it on March 12, 2021.

Hugh Y. Cai and Allison Cai looked through GISAID (which has 10 million sequences for the coronavirus) and published a research paper on the outbreaks in Michigan and Wisconsin in the Journal of Veterinary Diagnostic Investigation in June 2021.

In April 2021, months after the CDC's discovery, The Detroit Free Press and the Documenting COVID-19 Project were among the few US news outlets to report on the infections.

Other emails show that officials in Illinois were so concerned about the outbreak from the Michigan farm that they did not feel safe taking in their mink pelts. However, Illinois did eventually take approximately 17,000 pelts in November 2021.

Scott Weese, director of the Centre for Public Health and Zoonoses at the University of Guelph, in Canada, believes that it was important for the CDC to report outbreaks immediately to keep the global public health community informed and safe.

Weese told China Daily: "The other aspect, though, is international communications because this pandemic doesn't respect boundaries. We learn a lot by seeing what happens in other countries. If we don't hear about what's happening, we can miss opportunities to intervene. So, failure to spread the information to public health colleagues internationally could have had a negative impact."

Michigan has 12 mink farms with about 22,000 animals, according to 2017 data from the USDA.

Sutfin said that people who live in Michigan and the surrounding areas were not in danger in 2020 from the cases of animal-to-human transmission of COVID-19.

"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," she said.

"As close contact with mink would be needed for the virus to spread from mink to humans, the risk to people outside farms including those living in nearby areas is likely very low."

The only other cases of animal-to-human transmission of COVID-19 have involved a pet hamster in Hong Kong and a white-tailed deer in Canada.