Dutch authorities announced this week that they suspect a mink has transmitted the coronavirus to a worker at a fur farm in the Netherlands. If confirmed, this would be the first concrete evidence of a specific species passing the virus to a human.
Analysis found strong similarities between the virus in the worker and in the minks, making it plausible that the virus jumped species. “Based on this comparison and the position of that form of the virus in the family tree, the researchers concluded that it is likely that one staff member at an infected farm has been infected by mink,” the Dutch government said in a statement.
Mink on at least three farms in the southern part of the country have tested positive for the coronavirus, according to Lisa Gaster, a spokesperson for the Ministry of Agriculture, Nature and Food Quality.
“The take-home message now is we are still learning a lot about COVID-19, this coronavirus, and the animals it can infect,” says virologist Brian Bird, a veterinarian and associate director of the University of California Davis One Health Institute. Bird, who is not involved in the Dutch response, cautions against undue alarm. “The risk here is related to direct contact or proximity to farmed mink, and certainly the general population has very little contact with those animals at those settings.”
Bats are widely believed to be the likely reservoir for the novel coronavirus, since the genome of a closely related virus found in horseshoe bats is 96 percent identical to the coronavirus now circulating in people. But scientists haven’t yet established that the virus jumped directly from bats to humans. That may be impossible to prove unless they discover SARS-CoV-2—the coronavirus that is circulating among people—in a bat in the wild. It also remains unknown whether an intermediary host, such as pangolins, may have transmitted the virus to humans. (Read more about the quest to find the next potential coronavirus animal host.)
There are more than 800,000 mink living on Dutch farms and, according to the Ministry of Agriculture, Nature and Food Quality, the industry brings in about $100 million dollars a year. In the wild, the weasel-like animals live in or near water. Their soft fur has long been coveted for clothing, particularly in China, the top importer of mink pelts.
In 2016, there were more than 150 fur farms in the Netherlands that produced six million mink pelts, according to Humane Society International, but those fur farms are being phased out. Starting in 2013, the government prohibited the opening of new mink farms, and all existing facilities are required to close by 2024. PJ Smith, director of fashion policy at Humane Society International, says this mink coronavirus development could hasten the closures. He describes mink farms throughout Europe as akin to factory farms for poultry and pigs. “They have rows and rows of cages kept in barns where thousands of mink are kept. Several animals are kept in each cage, and their waste falls through wire bars onto the ground.”
Even if the mink-to-human transmission is confirmed as the first known animal-to-human case, Dutch officials emphasize that there’s very little risk to the general public from this incident or from fur farms in general. Testing at mink farms by the Bilthoven-based Dutch National Institute for Public Health and the Environment has shown no evidence of the virus in dust or air molecules outside the sheds that house the animals.
Last month, after mink at some Dutch farms were found to have coronavirus, authorities banned removal of mink, manure, or any other animals from infected farms. Officials initially thought minks at the farms contracted the virus from humans, but based on genome analysis they now think a farm worker got sick from the mink.
This week, the government also reported that feral cats may be spreading the virus between fur farms, noting that the pathogen identified at two infected farms looked closely related and that three out of 11 cats that roam the grounds of one farm had antibodies to the coronavirus. “Pending further research, mink-farm owners are advised to ensure that cats cannot enter or exit the site,” the government said.
The farm worker who contracted the coronavirus has recovered. Meanwhile, authorities are introducing new health and safety regulations. Mink on all farms will now be tested for coronavirus antibodies to ascertain how prevalent the virus has been in those settings. At farms found to have infected animals, visitors aren’t allowed into mink sheds, and employees must use personal protective equipment. In addition, farms must report to the government any case of a mink showing symptoms of COVID-19.
Dutch researchers are now comparing genetic samples taken from the sick farm worker, from infected people in the area around that farm, and from infected mink in an effort to trace the family tree of the virus and better understand the chain of transmission.
The government is taking appropriate steps, but other species may also require monitoring in the future if we learn about other infected animals, virologist Brian Bird says. “We need to keep an open mind and keep our radar tuned high.”
Update, May 29, 2020: Dutch authorities confirmed that a second case of likely mink-to-human transmission occurred at another mink farm, where three workers have tested positive for the coronavirus. Scientists can't establish with available data whether one person was infected by a mink and then spread the virus to coworkers, or whether the others also got it directly from the animals. The genetic code of the virus found in the workers doesn't match samples taken from patients throughout the Netherlands, which suggests it likely came from another species.
Update, June 4, 2020: Starting June 5, all the minks at nine Dutch fur farms where some animals have been infected with the coronavirus will be killed. The animals, numbering in the thousands, will be culled within a week, according to the Dutch government. Minks are only allowed to be killed by gassing them with carbon monoxide in the country.
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