Dr. Yan's trajectory was carefully crafted by Guo Wengui, a fugitive Chinese billionaire, and Stephen K. Bannon, a former adviser to Mr. Trump.
They put Dr. Yan boarded a plane to the US, gave her a place to stay, trained her on media appearances, and helped her interview well-known conservative television presenters like Tucker Carlson and Lou Dobbs who have shows on Fox. They used what appeared to be a deep belief that the virus was genetically engineered and uncritically accepted what evidence it provided.
"I said from day one there were no conspiracies," Bannon said in an interview. "But there are no coincidences either."
Mr. Bannon noted that unlike Dr. Yan did not believe that the Chinese government "did this on purpose". But he has advanced the theory about an accidental leak of risky laboratory research and intends to have a debate on the origins of the new coronavirus.
"DR. Yan is a small voice, but at least it's a voice," he said.
The media dealing with the Chinese diaspora – a jumble of independent websites, YouTube channels, and Twitter accounts with anti-Beijing leanings – has created a rapidly growing chamber of echoing misinformation. With few reliable Chinese language news sources to verify, rumors can quickly become a distorted reality. Increasingly, they feed on right-wing American media.
Wang Dinggang, who was led by Dr. Yan and a close associate of Mr. Guo contacted YouTube host who appears to have been the first to spread rumors about Hunter Biden, a son of President-elect Joseph R. Biden Jr., and Mr. Guo reinforced unsubstantiated claims about Hunter Biden's involvement in a child molestation conspiracy. They were picked up from Infowars and other American fringe stores. Mr Bannon, Mr Wang and Mr Guo all now support the misconception that the presidential election was rigged.
Big tech companies have started to push back as Facebook and Twitter try to improve police content. Twitter permanently banned one of Mr. Bannon's accounts for violating the rules of glorifying violence after suggesting on its podcast that the F.B.I. The director and Dr. Anthony S. Fauci, the nation's leading expert on infectious diseases, should be betting on pike.