One of the most popular topics on the Chinese microblog Weibo on Thursday was a one-minute clip of a US congressional hearing this week on how the country was dealing with the coronavirus.

In the video posted by the People’s Daily, Robert Redfield, director of the US Centers for Disease Control and Prevention, is asked whether there may have been deaths attributed to influenza that could actually have been the result of Covid-19. Redfield responds in the affirmative: “Some cases have been actually diagnosed that way in the United States today.”

Redfield’s vague answer was enough to add fuel to a conspiracy theory that has been gaining traction over the past two weeks in China – that the coronavirus did not originate in China but may have come from the US instead.

“The US has finally acknowledged that among those who had died of the influenza previously were cases of the coronavirus. The true source of the virus was the US!” one commentator said. “The US owes the world, especially China, an apology,” another said. “American coronavirus,” one wrote.

The theory has gained traction over the past few weeks, after a respected epidemiologist Zhong Nanshan, said in a passing remark at a press conference on 27 February that although the virus first appeared in China “it may not have originated in China”.

Zhong later clarified his statement, saying that the first place where a disease is discovered does not “equate to it being the source”. He told reporters: “But neither can we conclude that the virus came from abroad. Only through investigation and tracing can we answer that question.”

Yet only Zhong’s first comment has stuck, repeated by Chinese diplomats, state media and officials who have subtly encouraged the idea.

On Thursday, a foreign ministry spokesman suggested without evidence the US military might have brought the virus to the Wuhan, the centre of the outbreak. Zhao Lijian accused the US of lacking transparency, saying on Twitter: “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!”

China’s ambassador to South Africa said last week on Twitter that the virus was not necessarily “made in China”.

An editorial in Xinhua last week also echoed Zhong: “The epidemic was first reported in China but that does not mean it necessarily originated in China … The WHO has said many times that Covid-19 is a global phenomenon with its source still undetermined.”

Officials have framed the campaign as a protest against the “politicisation” of the outbreak by countries such as the US, where some officials have continued to use the terms “Chinese coronavirus” or “Wuhan virus,” despite the World Health Organization’s discouragement. But analysts say China may be looking to deflect blame as the coronavirus spreads around the world.

“We might be heading into first global recession caused by Chinese Communist party mismanagement,” wrote Bill Bishop, author of the China newsletter Sinocism. “Previous manmade disasters in China since 1949 never really spread outside the People’s Republic of China’s borders in meaningful ways.”

“This time looks to be different … And that is likely one of the reasons the propaganda apparatus and PRC officials are pushing so hard the idea that virus may not have originated in China,” he wrote.

For weeks, Chinese state media pointed to a seafood market in Wuhan as the likely origin for the virus while researchers said the source had not yet been determined, but few have floated the idea that it came from outside of China. Another respected Chinese researcher, Zhang Wenhong, said in an interview with the China Daily that he did not believe the virus had been imported into China.

“If that was the case, we should have seen patients emerging from different regions in the country around the same time rather than their concentration in Wuhan,” he said, in comments that later appeared to have been removed from the interview.

“I think the consensus is still clearly that the virus did originate in China,” said Jane Duckett, professor at the Scottish Centre for China Research, University of Glasgow, focusing on Chinese policy and health.

“This would appear to be a nationalist narrative aimed at countering criticism of the Chinese government for not better managing the outbreak in its early stages,” she said.

Shifting the narrative may also be important as China tries to move forward, now that new infections appear to have levelled off. This week, the Chinese leader, Xi Jinping, visited Wuhan for the first time since the outbreak began as state media pronounced “victory is near”. State media showed elaborate celebrations marking the closure of the last of the temporary hospitals in Wuhan.

“This is a propaganda effort aimed at the domestic audience. Among the Chinese public, there is a general awareness that delays in notifying the public led to many more infections in Wuhan,” said Victor Shih, a politics professor at the University of California, San Diego.

He said: “This campaign is aimed at distracting the public from the party’s delayed response.”