Some people do not know what the word probabile means because in their world there is only certainty. I have never heard a scientist categorically discarding any other possibility. My understanding is that according to them bats were most likely the reservoir for the virus, which upon mutation start infecting humans.
"Viruses are finely tuned to their hosts, but mutations can and have produced strains that can jump from animals into humans. Sara Sawyer, a virologist at the BioFrontiers Institute of the University of Colorado, Boulder, spoke to Nature about what a virus must do to make the leap between species, and describes a worrying discovery her laboratory has made regarding a future threat. How do animal viruses infect humans?
Most animal viruses cannot infect humans—we ingest viruses all the time, and most of them pass straight through. To do us harm a virus has to trick its way inside our cells, so it can use them as a factory for making more of itself. Animal viruses need to pull off several tricks to do this."
