Wherever there’s a “scientist”, or “doctor”, that’s where it’s going to come from.
Why does the next “pandemic” microorganism have to be a coronavirus? It could be any of a number of other pathogens that perhaps affect swine, or horses, or various other domesticated or even wild animals.
Cholera is one possibility, and in fact, as a water-borne disease, it was a serious problem in Colonial America. With a little tweaking, it could be made into a serious threat to humanity once again. Or diptheria. Or typhus or typhoid fever.
There are more ways to spread mischief than people even think about.