1. Direct-jump from bat population
2. Started in bats, came to humans through intermediate animal
3. Came from frozen food outside of China
4. Lab accident.
I used to think the lab accident theory was crazy, because it sounds like a science fiction movie. Not an impossible theory, just a crazy one.
But according to this article, despite a year of investigation, (1) is unlikely because we haven't found anyone that interacted with the nearest bat population hundred of miles away that didn't work in the virus lab in Wuhan and that caught the virus, (2) is unlikely because we would have found the intermediate animal by now, (3) is unlikely because the first case found was in China (and not somewhere else... if frozen food had the virus, the food would have had it before it was frozen, and someone else would have had it), and (4) is unlikely because a government famous for blocking information and is paranoid about how it is perceived domestically and internationally says "No, trust us on this one."
At some point, crazy theories become the most likely. Hopefully I'm wrong though, and they find an explanation that isn't "lab accident." It seems like we should be studying viruses and sharing that information with each other, and accidents like this will make it more likely that such research doesn't happen.
When you think about how common the basic symptoms are, I think it could take quite a while before someone wondered whether it was different from the common cold and went testing.
IMO Its a perfectly reasonable theory that it was spreading slowly through China for months, from some distant province, and it wasn't recognised as a new virus until it arrived somewhere there was the expertise to look at it in the right way.
That would mean that the reason it was found in Wuhan and not anywhere else is just because Wuhan was the first place with people who had the expertise and the interest to investigate and figure out it was new.
Whatever the truth is, that is just as good a theory as any other, and it explains the apparent evidence for the virus appearing a few months earlier in some countries.