Mass cullings take place as mink farms identified as hot spots for the disease

In what researchers believe is a world first, genetic analysis has confirmed the transmission of the novel coronavirus from human to animal and back to humans again during COVID-19 outbreaks on Dutch mink farms.

Using whole genome sequencing, virologists in the Netherlands verified that the animals were susceptible to infection, and were responsible for passing on the virus to other workers during viral flareups that infected dozens of people at several farms over the summer.

The research, which was published on the preprint server BioRxiv and has not been peer-reviewed, was conducted at the virology department at the Erasmus Medical Center in Rotterdam.

"To the best of our knowledge, these are the first animal to human SARS-CoV-2 transmission events documented," stated the study, which was led by Marion Koopmans, who is head of virology at Erasmus. "More research in minks and other mustelid species is needed, to demonstrate if these species can be a true reservoir of SARS-CoV-2, although from our observations we consider this likely."

Several animal species are known to be susceptible to the novel coronavirus, including but not limited to dogs, cats, ferrets, hamsters, rhesus monkeys, rabbits and fruit bats. Epidemiologists have stressed the importance of monitoring animal populations which may harbor the virus and even cause so-called spillover events, where pathogens are transferred to humans from other species.

"Continued monitoring and cooperation between human and animal health services is crucial to prevent the animals serving as a reservoir for continued infection in humans," the authors of the study said.

The Netherlands is one of the world's leading producers of pelts from mink, which are also farmed on a large scale in China, Poland, and Denmark. But the Dutch mink fur trade has been decimated during the pandemic.

The virus was first detected on two mink farms in the Netherlands in late April, following routine monitoring by animal health services.

"We conclude that the virus was initially introduced from humans and has evolved, most likely reflecting widespread circulation among mink in the beginning of the infection period several weeks prior to detection," the study said.

The virus spread rapidly through more than 20 mink farms in the Netherlands, and has also been detected on farms in Spain and the United States.

More than 1 million minks have now been culled in the Netherlands to control COVID-19 outbreaks, according to the Humane Society International, meanwhile Spanish authorities have ordered the killing of more than 90,000 minks at a farm in the Aragon region where an estimated nine in ten animals contracted the virus.