Mink-strain of COVID-19 virus in Denmark
On 5 November 2020, health authorities in Denmark reported 12 human cases of COVID-19 caused by a specific mink-associated variant strain of the SARS-CoV-2 virus. All 12 cases live in North Jutland and became unwell in September. Eight had a link to the mink farming industry and four cases were from the local community. Since June 2020, 214 human cases of COVID-19 have been identified in Denmark with SARS-CoV-2 variants associated with farmed minks, including 12 cases with a unique variant. This particular variant strain displays a combination of mutations not previously documented. Laboratory tests conducted in Denmark indicate that this strain may have reduced response to neutralizing antibodies against SARS-CoV-2. These findings are preliminary and further studies and international collaboration are ongoing to confirm them.
Denmark has assessed that the ongoing circulation of SARS-CoV-2 in mink farms, the susceptibility of the mink, and the ease of transmission at the human-animal interface represents a risk to public health in the country. Genetic changes in the variant that may affect the risk of reinfection in humans, as well as COVID-19 related diagnostics, therapeutics and vaccines, are an additional concern. More scientific and laboratory research is needed to assess these issues. Denmark has shared the sequences of the strain to the GISAID genetic sequence repository to help researchers determine the significance of the mutations.
COVID-19 spreads primarily through human-to-human transmission, but transmission has also been observed between humans and some animals, such as mink, dogs, domestic cats and lions. Mink farms, in several European countries, including Denmark, Spain, Sweden, Italy and the Netherlands, have shown that the virus can move between mink and human. It is always a concern when a virus moves from animals to humans as genetic changes can happen as it moves back and forth.
The variant strain of SARS-CoV-2 was detected following enhanced surveillance in communities around mink farms undertaken by the Danish State Serum Institute (SSI) of the Ministry of Health. To prevent further spread of this and other mink-associated strains in people, the Danish authorities have announced a range of measures, including the culling of all remaining mink in farms in Denmark. Other public health measures include enhanced COVID-19 disease surveillance, increased sequencing of SARS-CoV-2 strains across Denmark, and extensive public health and social measures including movement restrictions for the populations in the seven municipalities in the north-west of Denmark that are affected, to reduce local transmission.
Available evidence has so far not indicated any changes in the virus affecting virus transmissibility, or disease severity associated with this new variant strain.
WHO response
WHO/Europe convened a meeting with Danish authorities and the European Centre for Disease Prevention and Control (ECDC) on 5 November to understand and discuss the details of the findings, and offer support.
WHO will coordinate further discussions with virology expert networks and follow up with other mink-producing countries. It will also continue to monitor transmission between animals and humans to assess any potential risks posed to public health.
Virus changes
It is normal for viruses to mutate or change over time. WHO has been following genetic changes in the COVID-19 virus since the start of the pandemic through a dedicated COVID-19 virology working group. When a virus moves from humans to animal populations such as mink, and back to humans, it can acquire unique mutations. Detailed analyses and scientific studies are needed to better understand the recently reported mutations.