As coronavirus cases dwindle in China, and explode across the rest of the world, Beijing is undertaking a campaign to shift blame for the emergence of the disease to a familiar foe — the United States.

The seemingly coordinated effort to, at minimum, sow doubts about the virus’s origin, and, at its most extreme, to directly accuse the U.S. military of creating and spreading the pathogen, has come from Chinese medical leaders, ambassadors and Foreign Ministry spokespersons — not to mention the hundreds of thousands of comments on Chinese social media echoing the conspiracy theories.

The undertaking is part of a broader campaign to deflect blame for the pandemic and China’s delay in taking action early in the emergence of the disease, which global experts say began in Wuhan, Hubei Province, potentially as early as November, and has infected more than 160,000 worldwide and killed nearly 6,000.

The first signs of Chinese skepticism of the virus’s origin came from the face of its fight against the epidemic, the celebrated doctor Zhong Nanshan, who was instrumental in the 2003 handling of the SARS crisis and has been featured in numerous televised interviews during the COVID-19 outbreak. At a press conference on Feb. 27, Zhong stated that the virus “may not have originated in China.”

Soon after, numerous Chinese politicians began what appeared to be a coordinated campaign to spread that idea, with several tweeting or uttering nearly identical statements questioning the origin of the virus.

On March 8, the Chinese ambassador to South Africa tweeted that, “Although the epidemic first broke out in China, it did not necessarily mean that the virus is originated from China, let alone ‘made in China.’ ”

Days later, the clearest salvo in the conspiracy campaign came from China’s Foreign Ministry spokesperson, Zhao Lijian, who tweeted: “CDC was caught on the spot. When did patient zero begin in US? How many people are infected? What are the names of the hospitals? It might be US army who brought the epidemic to Wuhan. Be transparent! Make public your data! US owe us an explanation!”

U.S. Department of Defense press secretary Alyssa Farah replied to Zhao’s tweet by saying, “As a global crisis, COVID-19 [should] be an area of cooperation between nations. Instead, the Communist Party of China has chosen to promulgate false & absurd conspiracy theories about the origin of COVID-19 blaming U.S. service members. #ChinaPropaganda.”

The State Department then summoned China’s ambassador in Washington in protest of the rumor. The assistant secretary of state for the Bureau of East Asian and Pacific Affairs, David Stilwell, expressed “stern representation” of the American position to Ambassador Cui Tiankai, who was “very defensive,” the State Department later said.

But conspiracy theories about the emergence of the virus aren’t limited to Chinese officials.

Last month, U.S. Sen. Tom Cotton insinuated on Fox News that, because Wuhan is home to one of China’s leading high-level biosafety laboratories, “we have to get to the bottom of” whether the virus emerged from that facility. (The Arkansas Republican later qualified his comments, saying the bioweapon theory is just one among several possible explanations.)

Meanwhile, three prominent Iranian officials, including former President Mahmoud Ahmadinejad, unequivocally asserted that the virus was a manufactured bioweapon. Ahmadinejad wrote a letter to the UN secretary-general, which he posted on Twitter, adding, “It is clear to the world that the mutated coronavirus was produced in lab.”

Iran has been one of the hardest-hit countries outside of China by COVID-19.

China’s state media have been equally involved in spreading skepticism of the virus’s origin. Official Communist Party publication Xinhua has published several articles questioning COVID-19’s provenance, and the state-run Global Times wrote, “As the U.S. COVID-19 situation becomes increasingly obscure, the Chinese public shares the suspicion raised by Zhao Lijian that the U.S. might be the source of the virus and that the U.S. is subject [to] questioning and is obliged to explain [its role to] the world.”

None of the numerous public figures and media outlets positing the alternative theories has provided evidence for their claims.

President Trump has been less critical of the rumors. On the same day his State Department and Pentagon officials were responding forcefully against the Chinese comments, the president praised Beijing’s sharing of information with the U.S. and said the rumors did not comport with his conversations with President Xi Jinping. However, he later told a press conference at the White House, “They [the Chinese] know where it came from. We all know where it came from.”

China’s campaign is targeted at both domestic and foreign audiences, according to Western experts. “I think both,” China specialist Bill Bishop told MarketWatch. “Globally to avoid being blamed for the carnage it is causing in so many countries, domestically to once again [blame] an external force as a way to deflect blame.”

While that may be a hard sell to foreign audiences, especially in America, Bishop, who authors the Sinocism newsletter and is a former MarketWatch executive, believes the rumors could gain much more traction at home in China. “I think plenty of Chinese will buy it,” he said.

But he sees this as bigger than simply a public health disaster. “Might this be the first global recession caused by CCP [Chinese Communist Party] mismanagement? Previous Communist Party–led disasters in China since 1949 never really spread outside the PRC’s borders in meaningful ways. Not this time.”

Several calls and emails to China’s Foreign Ministry, and direct messages to spokesperson Zhao, went unreturned.

Tanner Brown is a writer for MarketWatch and Barron’s and producer of the Caixin-Sinica Business Brief podcast.