When SARS broke out in 2002 the first case was an animal handler on a medium size farm in Foshan, 50 miles upriver from Hong Kong. Our best guess is that the domesticated animals were infected by wild rodents. The initial spread of the SARS virus infected farm workers, butcher shop workers, grocery store workers, and people at farmers markets.
https://en.wikipedia.org/wiki/SARS#Outbreak_in_South_China