Covid-19 Virus Infected With Polish Mink Has Specific Mutations

Identifying possible viral pathogen hosts and studying the spreading dynamics of the hosts in their populations are key steps to control zoonotic diseases. The origin of the COVID-19 virus may be bats, but the potential intermediate host has not been confirmed. The COVID-19 virus seems to spread easily between humans and other animal species, especially carnivores (ie, dogs, cats, ferrets, lions, cougars), which has raised concerns about new animal sources of the COVID-19 virus.

In November 2020, the human infection with the mutated COVID-19 virus on mink has attracted much attention. According to the British "Guardian" report on November 18, 2020, there were already Denmark, the Faroe Islands (Denmark's overseas autonomous territories), Seven countries and regions including the Netherlands, South Africa, Switzerland, Russia, and the United States have reported cases of mutated COVID-19 virus infections related to mink.

Recently, researchers from the University of Gdansk in Poland, the University of Helsinki in Finland and the Medical University of Gdansk in Poland published an article titled “COVID- 19 "Research on Virus Infection" article. After investigating the COVID-19 virus infection in a farm in northern Poland, the researchers found that the COVID-19 virus was present in the farmed mink. They speculated that the virus had been introduced to the farm before the end of September 2020.

Researchers performed reverse transcription PCR, antigen detection, and second-generation sequencing on 91 North American mink throat swab samples collected from a farm in northern Poland in November 2020, and used two different sequencing technologies to detect the mink COVID-19 virus. The genome was analyzed.

The analysis results showed that 15 minks (16.5%) tested positive for COVID-19. In all the virus isolates obtained, there are specific mutations in the two sites of the spike protein G75V and C1247F. Among them, the G75V mutation is located in the N-terminal domain, which may be responsible for the interaction with the host receptor or stabilizing the spike protein in a constrained pre-fusion state. However, so far, in other COVID-19 virus sequences stored in the Global Influenza Shared Database (GISAID), these two mutations have not existed at the same time.

The researchers also checked the genome sequences of 12 COVID-19 virus originating from mink to detect mink-specific mutations detected in the mink in the Netherlands and Denmark earlier, but no mutations were found. This result indicates that the COVID-19 virus from Polish mink was introduced separately. In addition, in the Polish mink COVID-19 virus isolate, the researchers also found five other proteins: non-structural protein (NSP) 2, NSP3, NSP14, NSP15 and nucleocapsid protein.

On the basis of the data set, the researchers inferred the phylogenetic relationship of virus strains by estimating the divergence time between each isolate. They estimate that the latest common ancestor of the COVID-19 virus from Polish mink and the two most similar sequences (Germany/NW-HHU-340/2020 and Norway/4235/2020) diverged on approximately September 31, 2020. After identifying the mutation in the amino acid sequence, the researchers believe that if the virus began to mutate after entering the Polish farm, then this event is estimated to occur around October 4, 2020. Therefore, they speculated that the virus had been introduced to the farm before the end of September 2020.

Researchers believe that humans living near mink farms should be extensively monitored to look for possible virus spillovers and new virus variants. Continuous epidemiological surveillance is a key step in preventing new outbreaks of zoonotic diseases.