Good article.

Depends on how you define "accident". Every natural mutation is an "accident". If it is a "good" accident, then it stands a chance of becoming permanent.
"Bad" accidents usually do not survive in the long run.
If, as seems likely, the virus came from something like a farmed animal or bat, it has probably been happening frequently for a long time, with no ill effects because the virus simply found itself in a hostile environment in which it was trapped and unable to persuade it's host's cells to reproduce it. Remember, unlike a bacterium, a virus is too elementary to be able to reproduce by itself.
.... until an accident happened. A virus mutated, by accident, and discovered it could now persuade its human host to reproduce it's genetic code, complete with the new mutation. From now on, it could sometimes transmit from human to human. Then it had another accidental mutation, which made it more efficient and virulent.

If viral transmission from animal to human is not a biological accident what the fuck is???

Stop the scare tactics ! Give reference(s) to one-or-more high-level epidemeologists who thinks thinks this is a reasonable idea (good luck with that).