Chinese Wuhan virus didn't originate in any markets. The first patients to become infected never had any contact with those markets in any way. China
There is a corona virus research lab in Wuhan, most likely explanation is the staff improperly disposed of trash or didn't take enough precautions. It's just standard communist incompetence.
Also
@XShrike - Fun fact: The American tv show Lassie was based on a novel about a female Collie. When it was made into a tv show, it starred a male dog playing the part, and they still referred to the Lassie character as a girl. Because males have brighter coats and it showed up better on black and white television screens.
If the Seton author knows that bit of trivia, it might have a couple layers of comedy not easily apparent, lol.