Here's a genetic analysis that was widely shared last month, which points to an index patient in late November around Wuhan: https://bedford.io/blog/ncov-cryptic-transmission/

Here's an article from Feb 11th in the SCMP which notes 500 health care workers in Wuhan were infected with the virus:

https://www.scmp.com/news/china/society/article/3050077/leas...