On January 15, in its last days, President Donald Trump’s State Department put out a statement with serious claims about the origins of the Covid-19 pandemic. The statement said the U.S. intelligence community had evidence that several researchers at the Wuhan Institute of Virology laboratory were sick with Covid-like symptoms in autumn 2019—implying the Chinese government had hidden crucial information about the outbreak for months—and that the WIV lab, despite “presenting itself as a civilian institution,” was conducting secret research projects with the Chinese military. The State Department alleged a Chinese government cover-up and asserted that “Beijing continues today to withhold vital information that scientists need to protect the world from this deadly virus, and the next one.”

The exact origin of the new coronavirus remains a mystery to this day, but the search for answers is not just about assigning blame. Unless the source is located, the true path of the virus can’t be traced, and scientists can’t properly study the best ways to prevent future outbreaks.

The original Chinese government story, that the pandemic spread from a seafood market in Wuhan, was the first and therefore most widely accepted theory. But cracks in that theory slowly emerged throughout the late winter and spring of 2020. The first known case of Covid-19 in Wuhan, it was revealed in February, had no connection to the market. The Chinese government closed the market in January and sanitized it before proper samples could be taken. It wouldn’t be until May that the Chinese Centers for Disease Control disavowed the market theory, admitting it had no idea how the outbreak began, but by then it had become the story of record, in China and internationally.

In the spring of 2020, inside the U.S. government, some officials began to see and collect evidence of a different, perhaps more troubling theory—that the outbreak had a connection to one of the laboratories in Wuhan, among them the WIV, a world leading center of research on bat coronaviruses.

To some inside the government, the name of the laboratory was familiar. Its research on bat viruses had already drawn the attention of U.S. diplomats and officials at the Beijing Embassy in late 2017, prompting them to alert Washington that the lab’s own scientists had reported “a serious shortage of appropriately trained technicians and investigators needed to safely operate this high-containment laboratory.”

But their cables to Washington were ignored.

When I published the warnings from these cables in April 2020, they added fuel to a debate that had already gone from a scientific and forensic question to a hot-button political issue, as the previously internal U.S. government debate over the lab’s possible connection spilled into public view. The next day, Trump said he was “investigating,” and Secretary of State Mike Pompeo called on Beijing to “come clean” about the origin of the outbreak. Two weeks later, Pompeo said there was “enormous evidence” pointing to the lab, but he didn’t provide any of said evidence. As Trump and Chinese President Xi Jinping's relationship unraveled and administration officials openly blamed the Wuhan lab, the U.S.-China relationship only went further downhill.

As the pandemic set in worldwide, the origin story was largely set aside in the public coverage of the crisis. But the internal government debate continued, now over whether the United States should release more information about what it knew about the lab and its possible connection to the outbreak. The January 15 statement was cleared by the intelligence community, but the underlying data was still held secret. Likely changing no minds, it was meant as a signal—showing that circumstantial evidence did exist, and that the theory deserved further investigation.

Now, the new Joe Biden team is walking a tightrope, calling on Beijing to release more data, while declining to endorse or dispute the Trump administration’s controversial claims. The origin story remains entangled both in domestic politics and U.S.-China relations. Last month, National security adviser Jake Sullivan issued a statement expressing “deep concerns” about a forthcoming report from a team assembled by the World Health Organization that toured Wuhan—even visiting the lab—but was denied crucial data by the Chinese authorities.

But more than four years ago, long before this question blew up into an international point of tension between China and the United States, the story started with a simple warning.

In late 2017, top health and science officials at the U.S. Embassy in Beijing attended a conference in the Chinese capital. There, they saw a presentation on a new study put out by a group of Chinese scientists, including several from the Wuhan lab, in conjunction with the U.S. National Institutes of Health.

Since the 2002 outbreak of SARS—the deadly disease caused by a coronavirus transmitted by bats in China—scientists around the world had been looking for ways to predict and limit future outbreaks of similar diseases. To aid the effort, the NIH had funded a number of projects that involved the WIV scientists, including much of the Wuhan lab’s work with bat coronaviruses. The new study was entitled “Discovery of a Rich Gene Pool of Bat SARS-Related Coronaviruses Provides New Insights into the Origin of SARS Coronavirus.”