“The most straightforward explanation for the ‘suspicious’ genetic traits is natural recombination with other coronaviruses,” Alex Berezow, a microbiologist, wrote in an article for the American Council on Science and Health.
Still, Dr. Yan’s explosive claims quickly went viral on social media. A video clip of her Tucker Carlson show appearance has gotten two million views on YouTube, and nearly a million views on Facebook. Conservative influencers like Dennis Prager, Mike Huckabee and David J. Harris Jr. have also shared her claims.
On Wednesday, Facebook and Instagram began flagging posts from Mr. Carlson’s show about Dr. Yan’s claims, saying that they repeated information about the coronavirus “that multiple independent fact checkers say is false.”
Twitter suspended Dr. Yan’s account on Wednesday, which provoked another round of viral posts, including accusations by Senator Josh Hawley of Missouri that Twitter was “openly on the side of Beijing.”
A Twitter spokesman declined to comment.
Public health authorities, including the World Health Organization and the Centers for Disease Control and Prevention, have also noted that while the exact source of the virus is still unknown, the evidence strongly suggests a natural origin. “The sequences from U.S. patients are similar to the one that China initially posted, suggesting a likely single, recent emergence of this virus from an animal reservoir,” explained a post on the C.D.C.’s website.
In addition, a closer look at Dr. Yan’s study — which appeared on the open-access site Zenodo, and was not peer-reviewed — raises questions about her political motivations.
The study’s first page lists support from the “Rule of Law Society Rule of Law Foundation,” a pair of anti-China organizations spearheaded by Guo Wengui, the exiled Chinese billionaire, and Stephen K. Bannon, President Trump’s former chief strategist, who was arrested last month on unrelated fraud charges. Neither organization has a history of sponsoring scientific research, and Mr. Guo and Mr. Bannon have spent months advancing baseless theories about the coronavirus’s origins.
The unproven theory that the virus originated in a Wuhan lab has become a popular talking point on the right. Mr. Trump and Mike Pompeo, the secretary of state, have advanced the theory, though U.S. intelligence agencies have not reached a conclusion on the issue.
Dr. Yan has become an increasingly popular guest on right-wing shows, and has made several appearances on Mr. Bannon’s “War Room” podcast this year, in which she echoed the points she made on Mr. Carlson’s show this week. In one July appearance, she claimed, without evidence, that the virus was engineered in a lab, and was “not from nature.”