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Of all the mysteries about the novel coronavirus, its origin excites the most fervent debate. At the outbreak’s beginning, there were conspiracy theories that the virus was man-made; recently, questions have focused on whether a natural virus was accidentally spread through research.

In the United States, such speculation largely comes from politicians hawkish against Beijing and keen to defend the Trump administration. Scientists, meanwhile, are often the most hesitant to speak out, wanting to focus on research that helps end the outbreak — not who, if anyone, caused it.

But the theories have spread widely, prompting a response from U.S. officials and President Trump himself. So, here is a skeptic’s take on three rapidly mutating theories: one clearly false, one possible but not supported by known evidence and one broadly true.

1. The outbreak was linked to bioweapons research

As China placed Hubei province under lockdown in January, the Washington Times, a conservative U.S. newspaper, cited research by former Israeli military intelligence officer Dany Shoham to argue that “Coronavirus may have originated in lab linked to China’s biowarfare program” in Wuhan, the Hubei capital.

That article suggested that the Wuhan National Biosafety Laboratory and the Wuhan Institute of Virology had been working on biological warfare. Both institutions are real — they were hardly secretive — but there is no evidence of this. When contacted by The Washington Post for a Jan. 29 article, Shoham refused to comment further.

Experts suggesting that the virus was man-made relied on a shoddy understanding of the science. “Based on the virus genome and properties there is no indication whatsoever that it was an engineered virus,” Richard Ebright, a professor of chemical biology at Rutgers University, told The Post.

Robert Garry, a virologist at Tulane University in New Orleans, later told Science News in March that the virus was fundamentally unlike something that would have been designed. “It has too many distinct features, some of which are counterintuitive,” he said.

Despite this, a Pew poll released last week found almost 3 out of 10 Americans believed the virus could have been made in a lab; Those on the Republican side of the spectrum were twice as likely to believe this as Democrats.

2. The novel coronavirus leaked from a lab accidentally

As the bioweapon theory subsided in February, it was replaced by a more plausible alternative: That a virus from a natural source could have leaked accidentally from one of Wuhan’s laboratories.

This idea attracted high-profile political support. “We don’t know where it originated, and we have to get to the bottom of that,” Sen. Tom Cotton (R-Ark.) told Fox News in mid-February, before dismissing early suggestions that the virus had spread at a Wuhan market. “We also know that just a few miles away from that food market is China’s only biosafety level 4 super laboratory that researches human infectious diseases.”

Some scientists don’t dismiss this outright. In January, Ebright did not want to talk on the record about the idea of a leak because it was too speculative. He changed his mind and this week told The Post that he thinks it “at least as probable” as an incident outside of a lab, a position other scientists disagree with.

There is circumstantial evidence. Researchers at the Wuhan branch of the Chinese Center for Disease Control and Prevention did conduct research on bat coronaviruses, which some viewed as risky. The State Department expressed concern about the safety standard of the Wuhan labs in at least two cables, The Post’s Josh Rogin reported this week.

But that does not prove that the novel coronavirus was ever studied in Wuhan, nor that it leaked. “There is no evidence of escape from a lab,” Andrew Rambaut, a microbiologist at the University of Edinburgh, wrote in an email. “The virus is just like a virus we would expect to see in wild bat populations, similar viruses have jumped from non-human animals to animals in the past, so I see no reason to speculate about this any further.”

3. The Chinese government misled the world about the coronavirus.

With no direct evidence of a leak from a laboratory, Cotton and others have noted that China has blocked the release of information about the early days of the outbreak. This is true: The Post reported on China’s obfuscation of information about the outbreak as early as Feb. 1.

Beijing was slow to share data with outsiders, including experts from the World Health Organization. An investigation by the Associated Press published Wednesday found that Chinese officials withheld information for six key days, allowing the virus to spread without restriction at a crucial moment.

Chinese journalists have published articles that suggest officials undercounted the death toll in Wuhan. Scientific research that suggested China was the source of the outbreak has been withdrawn. Some Chinese officials, such as Foreign Ministry spokesman Lijian Zhao, have floated unfounded theories that the virus may have originated from the United States.

Academics who study Chinese propaganda say that the measures were an attempt to distract from early coronavirus failures. This can certainly be seen as a coverup, though Beijing is hardly the only government accused of withholding information related to the virus.

The U.S. government has considered these theories. The New York Times reported this weekend that intelligence agencies investigated but did not detect “any alarm inside the Chinese government that analysts presumed would accompany the accidental leak of a deadly virus from a government laboratory.”

Joint Chiefs Chairman Gen. Mark Milley confirmed that intelligence agencies were considering the origin at a briefing on Tuesday. “At this point it’s inconclusive, although the weight of evidence seems to indicate natural, but we do not know for sure,” Milley said.

At a news conference on Wednesday, Trump was asked an unusually specific question about the laboratory leak theory by John Roberts of Fox News, but he declined to answer.

Understanding from whatever mistakes were made in China could mean a new era of openness and cooperation between Washington and Beijing. Indeed, the State Department memos showed, the U.S. government used to help fund the laboratories in Wuhan — the Trump administration cut funding to a U.S. pandemic research program that worked with the Chinese labs in 2019.

In the face of a pandemic, it’s understandable that many are looking for someone to blame. But a cascade of small errors is more likely than one grand conspiracy. Learning from that may not be satisfying, but it could go a lot further in preventing this from happening again.

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