The rumor appeared shortly after the new coronavirus struck China and spread almost as quickly: that the outbreak now afflicting people around the world had been manufactured by the Chinese government.
The conspiracy theory lacks evidence and has been dismissed by scientists. But it has gained an audience with the help of well-connected critics of the Chinese government such as Stephen K. Bannon, President Trump’s former chief strategist. And on Sunday, it got its biggest public boost yet.
Speaking on Fox News, Senator Tom Cotton, Republican of Arkansas, raised the possibility that the virus had originated in a high-security biochemical lab in Wuhan, the Chinese city at the center of the outbreak.
“We don’t have evidence that this disease originated there,” the senator said, “but because of China’s duplicity and dishonesty from the beginning, we need to at least ask the question to see what the evidence says, and China right now is not giving evidence on that question at all.”
Mr. Cotton later walked back the idea that the coronavirus was a Chinese bioweapon run amok. But it is the sort of tale that resonates with an expanding chorus of voices in Washington who see China as a growing Soviet-level threat to the United States, echoing the anti-Communist thinking of the Cold War era.
Right-wing media outlets fan the anger. Beijing, with its heavy-handed censorship and stranglehold on information, unwittingly gives the conspiracy theories a boost.
The idea of the coronavirus as an escaped weapon has been carried through international news outlets like the British tabloid The Daily Mail and The Washington Times, which suggested that the virus was being developed as part of China’s biowarfare program.
Last month, Mr. Bannon invited Bill Gertz, a Washington Times reporter, to be a guest on the inaugural episode of his radio show “War Room: Pandemic,” a spinoff of his “War Room: Impeachment,” which defended Mr. Trump during the Senate impeachment trial.
“Bill Gertz had an amazing piece in The Washington Times about the biological labs that happen to be in Wuhan,” Mr. Bannon said on his Jan. 25 show. Mr. Gertz appeared on another show several days later to continue putting forward the bioweapons theory.
Fox News has also dabbled in the theory, in one article drawing a connection between a 1980s thriller by Dean Koontz that “predicted coronavirus.” The book is about a Chinese military lab that creates a biological weapon.
The Chinese authorities say the outbreak began in a market in Wuhan where wild animals were sold. The city is also home to a biochemical laboratory.
Although much remains unknown about the coronavirus, experts generally dismiss the idea that it was created by human hands. Scientists who have studied the coronavirus say it resembles SARS and other viruses that come from bats. While contagious, so far it appears to largely threaten the lives of older people with chronic health issues, making it a less-than-effective bioweapon.
Spreading that information are some well-known critics of the Chinese government like Mr. Bannon and Guo Wengui, a Chinese fugitive billionaire. The two have pledged to raise a $100 million fund to investigate corruption, help people they believe to be victims of Chinese government persecution and, in Mr. Guo’s words, take down China’s Communist Party.
Hours after Mr. Cotton made his comments on Fox News, Mr. Guo took to his own media platform, G News, to boast in a 30-minute video that he had predicted that China would manufacture a crisis like the virus outbreak.
“I said a year ago that Chinese Communist Party might create a massive humanitarian crisis or a natural disaster or a pandemic before it dies,” Mr. Guo said from his $68 million apartment on the edge of Central Park in New York.
“On a wall at the entrance to Wuhan P4 lab, there is a slogan: When you step into this building, you enter into Pandora’s box,” Mr. Guo added, referring to the high-security lab.
He claimed that the lab has military connections, including that soldiers from the People’s Liberation Army serve as guards. He did not offer proof.
Mr. Guo is no stranger to conspiracy theories. The website for G News — which carries the slogan “Truth, Freedom” — is populated with headlines like “Breaking news: China will admit coronavirus coming from its P4 lab” and “Dead: founder of Canada’s P4 Lab, key to Wuhan coronavirus investigation.”
He has also advanced other claims without evidence. In 2018, he claimed that HNA, a Chinese conglomerate, had played a role in the death of its co-chairman, Wang Jian, in an accident in France. The French authorities ruled Mr. Wang’s death an accident. The company declined to comment at the time on Mr. Guo’s claims.
Mr. Guo waged his war against the Chinese government from Facebook and Twitter for months, but then both social media platforms suspended his accounts after he posted the personal information of Chinese people online.
Mr. Guo has had more success as views about China in Washington have grown more sinister. Mr. Cotton on Sunday helped make them part of the American political establishment.
Speaking to the Fox News anchor Maria Bartiromo, Mr. Cotton suggested that a dearth of information about the coronavirus’s origins was raising more questions than answers.
“We don’t know where it originated, and we have to get to the bottom of that,” he said on the program “Sunday Morning Futures.”
After receiving criticism for lending credence to what has been largely considered a fringe theory, the senator took to Twitter to say that he did not necessarily think the virus was an “engineered bioweapon.”
That idea, he said, was just one of several hypotheses that included the possibility that the outbreak was a “deliberate release.”
He also said it was possible that the virus had spread naturally, “but almost certainly not from the Wuhan food market.”
Cao Li contributed research.