The recent news of the possible culling of 15 million farmed mink in Denmark over fears that they could spread SARS-CoV-2 to humans has much attention turned toward the relationship between mink and the virus. Now, a new report in Science reports on a similar situation of mink in the Netherlands. Studying the genome sequence of viral strains on 16 mink farms, the team’s work found virus transmission between human to mink, as well as from mink to human.

The work is published in Science in the paper, “Transmission of SARS-CoV-2 on Mink Farms Between Humans and Mink and Back to Humans.”

Previous research has shown that multiple different animals such as non-human primates, cats, ferrets, hamsters, rabbits, and bats can be infected with the SARS-CoV-2 virus. In addition, SARS-CoV-2 RNA has been detected in felids, mink, and dogs in the field.

In the Netherlands, the virus was first diagnosed on two mink farms in late April 2020. In response, the Dutch national response system for zoonotic diseases was activated, and an extensive surveillance system was set up.

The study describes an in-depth investigation using whole genome sequencing of outbreaks on the first 16 infected mink farms in the Netherlands Their analysis combined SARS-CoV-2 diagnostics, whole-genome sequencing, and in-depth interviews with farm workers.

Although several animals have been shown to be susceptible to SARS-CoV-2, the zoonotic origin of the SARS-CoV-2 pandemic is still unknown. The authors conclude that the virus was initially introduced from humans and has since evolved, most likely reflecting widespread circulation among mink at the beginning of the infection period several weeks prior to detection.

By the end of June, 66 of 97 (68%) of the mink farm residents, employees, and/or contacts tested had evidence of SARS-CoV-2 infection.

Analysis of the mink virus genomes on these farms revealed a diversity of sequences. These large clusters of infection were initiated by human COVID-19 cases with viruses that bear the D614G mutation, according to the authors.

Sequencing also revealed that some people were infected with strains of the virus with an animal sequence signature, providing evidence of animal to human transmission. Further analysis indicated no spillover to people living in close proximity to mink farms.

However, despite enhanced biosecurity, early warning surveillance, and immediate culling of infected farms, transmission occurred between mink farms in three big transmission clusters with unknown modes of transmission.

“More research in minks and other mustelid species is important to understand if these species are at risk of becoming a reservoir of SARS-CoV-2,” the authors wrote. “It is imperative that the fur production and trading sector should not become a reservoir for future spillover of SARS-CoV-2 to humans.”

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