Senator Tom Cotton (R-Ark.) has been on an absolute tear about coronavirus, calling for all Americans in China to “get out now,” demanding the U.S. implement an extensive travel ban targeting China proposing a “Manhattan Project-level effort to create a vaccine” ― a reference to the undertaking that produced the atomic bomb during World War II.

MESSAGE TO ALL AMERICANS IN CHINA: Get out—now. Contact our embassy or consulates if you need help. https://t.co/AG23B5vCTj — Tom Cotton (@SenTomCotton) January 30, 2020

Cotton also suggested the coronavirus could have come from a Chinese “super laboratory that works with the world’s most deadly pathogens,” boosting a debunked fringe theory circulating among tabloids and conservative media outlets. The conspiracy has gained attention on social media and appeared in a dubious article on right-wing site The Washington Times, whose single named source for the claim was a former Israeli military official suggesting the virus could be linked to a biowarfare program.

“I would note that Wuhan (the province where the ailment was first reported) has China’s only biosafety level-four super laboratory that works with the world’s most deadly pathogens to include, yes, coronavirus,” Cotton tweeted.

Health experts have rejected the suggestion that the virus is the result of some sort of bioweapon or other manufactured cause, calling it unfounded and nonsensical. A laboratory is located in Wuhan, but it’s a city of over 11 million and no proof has surfaced that the lab has any connection with the outbreak.

“It’s a ridiculous assertion,” said Dr. Michael Mina, assistant professor of epidemiology and immunology at Harvard University. “All signs point to a pathogen that has been circulating in animals and jumped to humans. It’s pretty common for these viruses and there’s no good reason for him to be saying something like that.”

Although Cotton’s views break with medical experts, they’re in keeping with his longtime opposition to the Chinese government, which he has called an “evil empire.” Cotton’s legitimate criticisms of China’s human rights record have morphed into his unfounded allegations against Beijing for failing to stop the spread of coronavirus through a “deadly combination of Chinese duplicity and incompetence.” China should face “serious consequences” for the outbreak, Cotton told Fox News.

But China has actually been fairly quick to address the virus and to alert international officials to the problem, according to health experts, and has as shared information on the virus that has helped epidemiologists study and track it. Although officials have expressed concerns about transparency around China’s handling of the outbreak, international health organizations and U.S. officials have largely praised China’s reaction to the crisis.

“They have done everything that you could hope for and is current-day standard practice that would be done in any other country,” Mina said.

The U.S. has also exercised extensive caution in handling the crisis, and on Friday the government quarantined 195 Americans who recently flew home from Wuhan.

The state department has issued travel warnings about trips to China, and on Friday several major U.S. airlines announced a suspension of all flights to the nation’s mainland. Some countries surrounding China, including Russia, Mongolia and Singapore, have taken steps to shut down their borders.

The outbreak has resulted in massive amounts of disinformation, viral social media falsehoods and online grifters attempting to cash in on the virus. Some conspiracy theorists have even promoted drinking dangerous bleach as a cure.

The virus has also led to anti-Chinese sentiment in numerous countries, prompting local officials and community organizations to denounce surging racism against Chinese communities.

“Misinformation around these outbreaks is definitely a problem,” said Dr. Tara Kirk Sell, senior scholar at Baltimore’s Johns Hopkins Center for Health Security. “When we undermine trust and get in the way of a public health response, those things can be really dangerous and really bad for trying to stop an outbreak.”

Health professionals and journalists have attempted to push back against the torrent of false information, debunking many of the myths around the virus and its origins. Although the outbreak is a global health emergency that has killed over 200 people and requires serious action, many infectious disease experts have urged patience while they assess the true dangers of the outbreak and cautioned against the kind of fearmongering that Cotton has embraced.

“Panic is never a useful thing to elicit in a population ... and anyone who’s doing that probably shouldn’t be in a public policy office,” Mina said.