Wuhan, China - the start
The epidemy started in Wuhan, China in January 2020.
First it had been thought that the origin is a seafood market, but later it was questioned. Anyway, there is some evidence that the seafood market has significantly contributed to the virus spread. As far as the market is concerned, there are issues there with extreme humidity and condensation as well. These markets have contributed to severe virus spread not only in Wuhan, but also in Beijing:
What I would like to add here is a view at the weather conditions.
Here are the weather graphs for the first 3 months of the year, with a couple of humid days in January when the epidemy began. Temperature often drops to dew point and relative humidity raises above 90%.
Under these circumstances condensation takes place resulting in foggy - cloudy air. Here are some of the Satellite photos show the deserted streets of Wuhan as the city enters its 8th day of quarantine in Januray, 2020:
