My understanding is that a zoonotic virus should undergo fairly rapid mutation after first appearing in a species. Like when SARS jumped to humans, it went through a period of rapid/frequent mutations. This seems to indicate that COVID-19 has actually been in humans for sometime, but undetected. Weird...
Anyway, interesting article discussing how the small mutations seen thus far are not a major concerns for vaccine development:
https://www.sciencedaily.com/releases/2020/08/200803105246.htm"The SARS-CoV-2 coronavirus is presumably already optimized to affect human beings, and this explains its low evolutionary change," explains Federico Giorgi, a researcher at Unibo and coordinator of the study. "This means that the treatments we are developing, including a vaccine, might be effective against all the virus strains."
