Experts have expressed concern that mink infected with Covid-19 that have escaped from fur farms could potentially spread the disease into the wild and infect other animals. There is currently no hard evidence that wild mink are spreading the virus, but it does raise the idea that SARS-CoV-2 might be circulating in a new zoonotic reservoir.
Following numerous Covid-19 outbreaks at fur farms in Denmark earlier this year, it became apparent that Covid-19 can spread from humans to mink, between mink, and from mink to humans. By early November, Danish authorities announced it would be culling its entire population of captive minks after numerous fur farms across the country experienced an outbreak of a Covid-19 variant, known as "cluster 5.”
Last week, an official at the Danish Veterinary and Food Administration told The Guardian that thousands of mink escape from fur farms each year. They are an invasive species and many are hunted and trapped in the wild each year. While health authorities recently claimed that “cluster 5” had “most likely” been eradicated from the fur farms, the possibility of escaped minks means that the novel coronavirus could potentially be circulating in the wild.
“Sars-CoV-2 could potentially continue to circulate in large-scale farms or be introduced to escaped and wild mustelids or other wildlife,” Professor Marion Koopmans, head of viroscience at Rotterdam’s Erasmus University who advises the World Health Organization (WHO), said in an email to The Guardian.
“In theory, as avian flu and swine influenza viruses do, continue to evolve in their animal hosts, constituting a permanent pandemic threat to humans and animals.”
Speaking to IFLScience, Professor Joanne Santini, a professor of Microbiology at University College London, commented: “Infected mink have been shown to transmit SARS-CoV-2 to other mink and to humans. There is, therefore, good grounds to be concerned that infected mink could transmit the virus to other at-risk animals. Mink are solitary animals so it’s unlikely that they would serve as a reservoir as they do when farmed, but they could transmit the virus to an animal that does live in high densities constituting a reservoir.”
Beyond Denmark, SARS-CoV-2 in mink has been reported on fur farms in the Netherlands, Spain, Sweden, Italy, and at least four states in the USA. Minks, like many other species, are susceptible to being infected with Covid-19. Due to the cramped conditions of mink fur farms, it’s especially easy for the virus to race through a captive mink population once it has entered.
The WHO has previously noted it is aware of the risk of the virus spreading to wild animals. Its investigation to track down the original animal reservoir of the SARS-CoV-2 virus — most likely a bat — aims to “prevent the establishment of new zoonotic reservoirs” of the disease.
It remains unclear how concerning this might be, however. Wildlife is known to serve as a reservoir of bird flu and swine flu viruses, which occasionally go on to infect farmed animals and humans. If the same happens to Covid-19, it’s possible — but not inevitable — that it could also become a permanent pandemic threat like swine flu or bird flu.
When asked whether the emergence of new zoonotic reservoirs would change the way the world handles the ongoing Covid-19 pandemic, Professor Santini added: "In short, yes.
“We not only need to prevent transmission from humans to animals, but we then need to contain any further transmission from animals to other animals and then back to humans. This will become extremely difficult if it has been transmitted to wild animals."