November 16-22 2020
Are mink a possible source of COVID-19 transmission?
The SARS-CoV-2 virus responsible for the Covid-19 epidemic could have its origins in animals. In order to enter a host’s cells, the virus attaches itself to a cellular receptor called ACE2. Given the similarities between the ACE2 receptors of different species, a certain number of animals could be liable to be infected by SARS-CoV-2.
Recently the virus has been detected on mink farms. Respiratory illnesses have been observed in the animals, as well as an increased rate in mortality, notably in the Netherlands, where these farms are numerous. In the first 16 mink farms infected by the virus, a study sequenced the virus’ complete genome and carried out diagnostic tests (PCR or immunology tests).
Analysis of tests carried out on different farms showed a probable “zoonotic” transmission of the virus – that is to say, between humans and mink. 68% of these farms’ employees were infected with SARS-CoV-2. In certain cases, employees initially tested negative when the mink were already infected, before testing positive a short time later. In addition, the viral genomes that infected the employees were very close to those that had infected the mink.
But could the mink virus reach local inhabitants? In reality, it was mainly the farm workers who were infected. The viral genomes of 34 locals living close to the farms were analysed. They reflected the general diversity of the virus circulating in the country, without having any specific similarities with the viral genomes of the infected mink. The conclusion was that the mink posed no particular threat of infecting local people.
Closeness of genome sequences in the Sars-CoV-2 carried by the mink compared to farm employees and the overall population.
We can see that the viral genome of employees is similar to the viral genome of the mink, since it can be found within the minks’ viral sequencing.
The significant variations in the genomes of the virus that infected mink suggests that the virus had been circulating for some times in these farms, in conditions that were favourable to its spread, notably the high density of animals. The mutations observed in the genome may suggest an adaptation of the virus in the host (the mink), leading to fears that this species of animal may become a reservoir for the virus. Supplementary studies will be necessary to confirm this hypothesis.