https://www.scientificamerican.com/article/four-generations-of-spread-seen-with-virus-in-china-alarming-experts/

Emerging data on the new virus circulating in China adds to evidence there is sustained human-to-human transmission in the city of Wuhan, and that a single case was able to ignite a chain of other infections.

The World Health Organization reported Thursday that there have been at least four generations of spread of the new virus, provisionally called 2019-nCoV, meaning a person who contracted the virus from a non-human source—presumably an animal—has infected a person, who infected another person, who then infected another person.