Zoonotic transmissible SARS-CoV-2 mutant identified in Danish mink

On Wednesday November 4th, Danish Prime Minister Mette Frederiksen announced that a zoonotically transmissible mutant strain of SARS-CoV-2 had been discovered on mink farms in northern Denmark[1]. The Danish State Serum Institute had reported their findings to the World Health Organization and the European Center for Disease Control a week earlier, although the data have not yet been published publicly. The novel strain reportedly shows reduced sensitivity to antibodies in laboratory tests and seems to have originated in the mink population. Thus far, 5 animals and 12 humans have tested positive for the mutant strain.

Zoonotic transmission could represent a significant new development in the COVID-19 pandemic. Although the SARS-CoV-2 virus is known to infect domestic species such as cats, ferrets, and dogs[2], there has been scant evidence to suggest animal-to-human transmission is a significant risk factor[3]. The first study suggesting zoonotic transmission was published by Munnink et. al. in September of 2020, in which the authors concluded that two Dutch mink farmers had likely contracted COVID-19 from infected minks[4]. The SARS-CoV-2 strains responsible for the zoonotic transmission in this study were not significantly divergent from human-to-human transmissible strains present in the Netherlands at that time. However, the authors noted that strain diversity in the mink population over time exceeded the expected mutation rate of approximately one mutation per 2 weeks, suggesting that the virus may mutate more rapidly in minks than in humans. 

The Danish government will initiate a mass cull of the country’s ~17 million minks to prevent further spread of the mutant strains. This decision could not have been reached lightly, as the mink fur trade is a billion-dollar industry in Denmark and represents a significant portion of their economy[5]. Farmers have struggled to balance safety precautions against the maintenance of their livelihood during the pandemic. Mink farms throughout the world have been forced to cull infected populations, with 2.5 million Danish minks culled in October alone[6]. However, the emergence of a zoonotic strain in an animal reservoir population has demonstrated that more drastic action is needed to ensure the efficacy of future vaccines and to prevent COVID-19 from becoming an endemic disease. As Prime Minister Frederiksen explained, “We have a great responsibility towards our own population, but with the mutation that has now been found, we have an even greater responsibility for the rest of the world as well.”