Francis Collins, the director of the National Institutes of Health, ducked out of his granddaughter’s swim meet into a dark recess of a Michigan high school, eager to hear from a team of scientists whether they thought a new coronavirus making a terrifying sweep across the globe could have been deliberately engineered.

It was Feb. 1, 2020, and nearly a dozen top international experts on viral genome evolution had convened for a teleconference. They had been scrutinizing the virus’s genetic sequence, which had been uploaded to the Internet three weeks earlier. A few were alarmed by some of the virus’s attributes, particularly how it clawed its way into human cells.

A day before the call, Kristian Andersen, a professor in the department of immunology and microbiology at Scripps Research in La Jolla, Calif., had written to Collins’s colleague Anthony S. Fauci, the director of the National Institute of Allergy and Infectious Diseases: “The unusual features of the virus make up a really small part of the genome (<0.1%) so one has to look really closely at all the sequences to see that some of the features (potentially) look engineered.”

Andersen wrote that he and three colleagues “all find the genome inconsistent with expectations from evolutionary theory. But we have to look at this much more closely and there are still further analyses to be done, so those opinions could still change.”

And they did. On that teleconference — the first known effort by senior U.S. and international health officials to determine whether human engineering or a laboratory leak might explain the emergence of the virus — most of the experts, including Fauci, concluded that the virus had probably evolved in nature and was transmitted from an animal to a human, Collins said in an interview.

The effort continued over the following weeks, when the scientists unanimously concluded there was no evidence of lab manipulation. The teleconference, which has not been previously reported, was the beginning of an ongoing, sometimes politicized and so far fruitless effort inside the U.S. government to determine whether the virus, SARS-CoV-2, could be the result of engineering or a lab leak.

Many more scientists would come not only to discount the “lab leak” theory but dismiss it as the unfounded projection of President Donald Trump, who in the pandemic’s early days publicly claimed the virus may have emerged from a lab in Wuhan, China, where the first known cases of the novel coronavirus were found.

Despite the early scientific consensus supporting natural origin, interest in the lab-leak theory never fully abated inside the U.S. government. Public health officials, intelligence officers and officials at the State Department and the National Security Council labored, with varying degrees of intensity and success, to understand the origins of the virus and whether it might have escaped from the Wuhan Institute of Virology, a world-renowned center for coronavirus research.

Most of what they learned came from public sources of information, including news articles, social media and scientific journals. Within the classified realm, a significant amount of the intelligence the United States obtained came from foreign governments, according to former officials with knowledge of the matter.

Last month, President Biden breathed new life into the origin mystery when he ordered intelligence agencies to redouble their efforts to determine whether the virus came from a lab and to report back to him in August.

Officials have said the review will examine all intelligence, including information that may have been missed during various inquiries during the Trump administration. A senior Biden administration official said a large amount of information remains unexamined — leading many former officials, who said they had searched far and wide, to conclude that the United States may have obtained new material.

This account of the government’s search for the virus’s origins is based on interviews with 28 current and former officials and experts, some of whom spoke on the condition of anonymity to describe internal deliberations and debates.

Despite Trump’s public claims that the virus came from a lab, the evidence has always been inconclusive.

“We never got to a smoking gun, which perhaps most people are focused on,” said Anthony Ruggiero, who was the NSC senior director for counterproliferation and biodefense in the Trump administration. “We were trying to do an all-source review of the information that’s out there and trying to do it in the most honest way possible, which is you start with some theories or hypotheses and then see where the information takes you.”

Some intelligence officers feared that senior Trump administration officials, frustrated that the spy agencies were coming up empty, were cherry-picking intelligence to support the lab-leak theory. Others worried that the intelligence agencies’ inability to determine the origin, despite their having warned for years of the likelihood of a devastating pandemic, revealed critical shortcomings that leave the country vulnerable to future outbreaks.

“I am not at all convinced that a natural origin is the only explanation; I’ve never been convinced,” Collins said. “And I do think we should be calling on China to make an expert-driven transparent investigation possible, because there are way too many unanswered questions.”

An early look at the virus

The team of experts that convened in February 2020 — hailing from the United States, the United Kingdom, Germany, the Netherlands and Australia — had compared the virus’s genome to that of RaTG13, a coronavirus discovered in horseshoe bats in China in 2013 and the closest known relative of SARS-CoV-2, with about 96 percent similarity. A few on the call believed some of the new virus’s signatures suggested possible human manipulation, while several others believed it looked like a naturally evolving one, Collins said.

Over the course of an hour, they discussed whether the virus’s “furin cleavage site” in its spike protein, which is key to the virus’s ability to attack human cells, could have been engineered. It was not present in the virus’s closest relatives, but it was present in other human coronaviruses, which to the experts suggested it was a feature that could occur naturally. The virus also has a number of other unique features that make it highly efficient at infecting humans — features those on the call thought a human could not possibly have designed.

“An expert trying to design an even more effective coronavirus would never have come up with this design,” Collins said, noting that the virus’s features were so unusual that a human could not have imagined them.

The group continued its collaboration, which led to a paper published as a preprint in February and then in the peer-reviewed journal Nature Medicine in March. In widely noted findings, five of the scientists concluded that their “analyses clearly show that SARS-CoV-2 is not a laboratory construct or purposefully manipulated virus.”

Collins said, “That was such a carefully done analysis that, barring the emergence of additional evidence — which we have not been able to see because the Chinese have obstructed the effort to gather the evidence — that’s where we were in March 2020 and where we are now.”

New investigations

While scientists scrutinized the virus’s novel features, national security officials began their own examination. Matthew Pottinger, the deputy national security adviser, put Ruggiero in charge of a small team at the White House that included a virologist, an epidemiologist and a researcher. Pottinger was frustrated when intelligence officials deferred to the Centers for Disease Control and Prevention and other public health experts to determine the virus’s origin, according to people who worked with him.

Ruggiero’s team examined mostly public information, including scientific papers and posts on Chinese social media. They largely relied on outside experts to analyze the virus’s features and determine whether they were more in line with a lab incident or a naturally occurring virus.

Experts say waiving patents won’t help poorer nations acquire the technical complexity of manufacturing coronavirus vaccines. (Luis Velarde/The Washington Post)

At the State Department, Miles Yu, the senior China policy official, was also scouring Chinese websites and social media channels. In April 2020, he gave a report to Secretary of State Mike Pompeo about what Yu considered circumstantial evidence that pointed to the lab as the source of the virus, former officials said. Yu was also suspicious of Beijing’s reaction to the outbreak, which seemed designed to block investigations, not assist them.

On April 30, the Office of the Director of National Intelligence issued a statement that made clear two theories were on the table.

“The [intelligence community] will continue to rigorously examine emerging information and intelligence to determine whether the outbreak began through contact with infected animals or if it was the result of an accident at a laboratory in Wuhan,” the statement said.

Many officials thought the ODNI’s comments put wind in the sails of the lab theory. But the statement also said that the intelligence community “concurs with the wide scientific consensus that the covid-19 virus was not manmade or genetically modified.”

That angered some officials in the State Department who had wondered whether the virus was designed as part of a secretive Chinese bioweapons program. To them, it appeared that the intelligence community might be siding with skeptical scientists on an unresolved question.

Speaking with reporters later that day in the East Room, Trump appeared surprised at the ODNI statement, which he said he had not read yet.

A reporter asked, “Have you seen anything at this point that gives you a high degree of confidence that the Wuhan Institute of Virology was the origin of this virus?”

“Yes, I have,” Trump said. Experts across his administration were searching for the origin. “You have scientific people, intelligence people, and others,” he said.

The reporter followed up, “And what gives you a high degree of confidence that this originated from the Wuhan Institute of Virology?”

“I can’t tell you that,” Trump said. “I’m not allowed to tell you that.”

It was a curious claim, since the president has the legal authority to declassify information.

Trump appeared eager to say more. Privately, he told aides that he believed the intelligence agencies had concluded that the virus came from the lab, according to a former White House official.

The agencies had never reached that conclusion.

Trump personally was “100 percent sure” the virus came from a lab, another former Trump official said, and wanted to declare it definitively in May or June. But he was talked out of that by his advisers, who still did not have sufficient evidence to make a conclusion one way or the other and worried about the repercussions of a baseless claim.

“Once again President Trump has been proven right, despite the bad advice of career bureaucrats,” Jason Miller, senior adviser to Trump, said in a statement last week in response to a request for comment from the former president.

Fruitless searches

Intelligence agencies continued to search for the origins, as well as for a “patient zero,” the first person to be infected with the novel coronavirus, two former officials said.

But the sources of information were thin and still mostly public.

Of the more limited amount of classified intelligence, a significant portion came from foreign intelligence services, four former officials said. They declined to identify the countries.

“Because we have friends that are willing to share, we don’t necessarily have to make redundant and duplicative efforts,” one former senior official said. “But there’s a liability to that when you’re dependent on other people’s information.”

Most intelligence officers are not virologists or epidemiologists. Short of finding an email or an informant that could show lab officials knew the virus leaked from their facility, it was unlikely that intelligence analysts were going to prove the theory, several former officials argued.

Pompeo, a former CIA director, was convinced of the virus’s origins. “I can tell you that there is a significant amount of evidence that this came from that laboratory in Wuhan,” he said on ABC News’s “This Week,” three days after Trump’s remarks.

By then he had received Yu’s analysis of Chinese social media that pointed to the lab.

One former senior official who worked closely with Pompeo said the secretary of state became fixated on proving a lab leak.

“He wanted a smoking gun, and we couldn’t give it to him,” the former official said.

No single piece of information had convinced Pompeo that the lab was the source.

“It’s the cumulative amount of evidence,” Pompeo said in an interview with The Washington Post last week. “It’s the absence of evidence for other theories, as well.”

Proponents of the lab-leak theory have pointed to the fact that scientists have not found an intermediate animal that could have spread the virus to humans. That process can take years, however; scientists still have not found an animal reservoir for Ebola, for instance. But the natural-origin theories also were not dispositive.

Pompeo said he was heartened to see renewed consideration of the theory. “I saw over a year ago that there was enormous evidence,” he said. “That enormous pile of evidence has increased.”

The fact sheet

Trump and Pompeo may have done more to slow the origins search than assist it.

“This issue became radioactive” after their public remarks, said one former official who believed the lab was probably the source of the outbreak.

But in the fall of 2020, a team at the State Department’s Bureau of Arms Control, Verification and Compliance turned its attention to the question. The bureau is legally mandated to investigate violations of disarmament treaties. Officials reasoned that if the virus came from a lab and, as some had suspected, was the product of the Chinese government’s bioweapons research, then the origins question fell within the bureau’s portfolio.

“When we started, we looked at both scenarios. And within the lab leak, we wanted to look at whether there was a [People’s Liberation Army] presence in the lab,” said David Asher, then a senior adviser in the bureau. Asher led a team that found information they believed showed the Wuhan lab had collaborated on publications and secret programs with China’s military since at least 2017.

The information was compelling but far from conclusive. “Simply knowing that there were secret military ties to the lab didn’t necessarily tell you where covid came from,” said David Feith, then the deputy assistant secretary of state for East Asian and Pacific affairs.

But in November 2020, the State Department team obtained classified intelligence it thought was a breakthrough: One year earlier, three researchers at the Wuhan lab had gone to a hospital with symptoms similar to those associated with covid-19 and other seasonal illnesses, such as the flu.

“The information about the sick workers was really striking,” Feith said. “If you had a cluster of illnesses and they were indeed covid, that could be your patient zero.”

There is no evidence that the researchers had covid-19, nor have their names been reported. It is not clear whether their blood was ever tested for antibodies that might prove they had the disease. And in China, it is not uncommon for ill people to seek routine care at a hospital. Fauci has called on China to release the medical records of the sick workers.

Several officials thought the information about the sick researchers was significant, and they wanted to make it public.

Pompeo was among them. Trump administration officials began the bureaucratic process of sanitizing the intelligence so it could be published without revealing sensitive sources and methods for how it was acquired. They also wanted to declassify reporting about Chinese military activity at the lab, as well as experiments involving RaTG13 — the coronavirus that Collins’s team of experts had compared to SARS-CoV-2 back in February 2020.

One former official said Pompeo wanted the intelligence community to issue a set of “talking points,” based on the declassified information, that would point to the lab. That would have been a significant change in the community’s position from the April 2020 statement, when two theories were being examined.

The provenance of the report on the sick researchers remains murky. Current and former officials have said it surfaced when a foreign source — it is not clear in which country — alerted U.S. officials to an earlier report in the U.S. government’s own files. That suggests there may still be information that analysts have missed.

The intelligence was released in the final days of the Trump administration by the office of the State Department spokesperson, not the intelligence community. The details in the “fact sheet,” as the document was titled, “just scratch the surface of what is still hidden about COVID-19’s origin in China,” it read in conclusion.

More may still be hidden. But had Trump officials found a smoking gun, they acknowledge, they would have said so.

Targeting China

Biden administration officials have never disputed the accuracy of the fact sheet, which was approved by officials at the State Department, the Pentagon, the White House and the ODNI.

But it is a document that has only a passing mention of the natural-origin theory: “The virus could have emerged naturally from human contact with infected animals, spreading in a pattern consistent with a natural epidemic.”

“These were limited, handpicked data points,” said a person familiar with the document.

The question to officials asked to clear the fact sheet was “Does this statement accurately reflect the underlying information, yes or no?” the person said, adding that the document did not seek to consider the range of possibilities for the origin of the virus.

A former official who signed off on the document confirmed that account.

Some government officials worried the review by the State Department arms-control bureau veered away from the facts, because it conflated the potential of an accidental lab leak with China deliberately engineering and releasing the virus.

Those tensions came to a head in the administration’s last days, when some officials wanted to declare that China was in violation of the Biological Weapons Convention, despite a lack of evidence to support such an explosive claim.

“They were trying to say it’s not just an accident but demonstrable of violations of the bioweapons convention, and that was a stretch based on the information that was available,” one former senior official said. “That was driving beyond their headlights.”

Barring some new, revelatory information, the Biden administration’s review of intelligence is unlikely to answer whether the virus came from a lab.

But Biden’s decision to look again has left former officials feeling vindicated for forcing evidence, however inconclusive, into the public debate. And with time, skeptical scientists who avoided politics have entered the fray.

“The Chinese government should be on notice that we have to have answers to questions that have not been answered about those people who got sick in November who worked in the lab and about those lab notebooks that have not been examined,” said Collins, the NIH director. “If they really want to be exonerated from this claim of culpability, then they have got to be transparent.”

Damian Paletta contributed to this report.