Just for the record (because the question keeps coming up): I don‘t think many - if any - real experts were convinced in early January that there was no human-to-human transmission of #SARSCoV2 just because China said so.
This is from a #covid19 story @sciencecohen, @dnormile and I published back on 9 January! Every researcher I talked to for that story (incl. @PeterDaszak and @MarionKoopmans quoted here) was skeptical about claim of no human-to-human transmission. 
To clarify: As several people have pointed out, China said there was no evidence for human-to-human transmission, not that that could be ruled out. I‘m just pointing out that experts assumed from the start that h2h transmission was likely.
