Hexapeptide vocabularies of the SARS-CoV-2 spike gene showed the shortest immunological T-distance to black rats.
Here we used a new method to search for the original host of the ancestor of the SARS-CoV-2 virus and for the donor of its gene for the spike protein, the molecule responsible for binding to and entering human cells.
Analyses suggest that the ancestral coronavirus adapted to bats was shortly passaged in treeshrews, while the donor of the spike gene was shortly passaged in rats before the recombination event.
Both treeshrews and black rats/mice live in Central China. All of these species may well be sold in Chinese wet markets and/or be used for passaging viruses in virological laboratories. Our results therefore do not answer the question whether the new virus is the product of a natural recombination of two viruses or the outcome of deliberate insertion of the gene for the spike protein into the genome of other coronavirus species.