What we know about the origin of covid-19, and what remains a mystery

Security personnel keep watch outside the Wuhan Institute of Virology during a 2021 visit by a World Health Organization team tasked with investigating the origins of the coronavirus. (Thomas Peter/Reuters)
12 min

The precise origin of SARS-CoV-2, the coronavirus that causes covid-19, remains unknown and continues to be a source of contentious debate. Two theories dominate the conversation: a natural spillover from infected animals, and a “lab leak” associated with coronavirus research in Wuhan, China, the city where the first cases of an unusual pneumonia-like illness were reported.

President Biden in May 2021 asked intelligence agencies to probe the origins of the virus, but they were unable to reach a consensus. Most favored, with “low confidence,” the natural spillover theory. Peer-reviewed scientific papers published last year bolstered the case that the virus came from animals sold at the Huanan Seafood Wholesale Market in Wuhan.

On March 20, an international team of scientists posted online a report, not yet peer reviewed or published in a journal, arguing that newly revealed data from environmental swabs at the market confirm that multiple animal species were present at the market, including raccoon dogs, known to be capable of coronavirus infections. The report claims that the new data “contribute to and underscore the large body of evidence supporting a natural origin of SARS-CoV-2.”

But critics of the natural spillover theory point out that investigators in early 2020 did not find any of these allegedly virus-infected animals that could have been the source of the outbreak. That fact was highlighted in a report issued last year by Republican staff on a Senate committee looking into the origin of the virus. The report also raised questions about safety protocols at a Wuhan laboratory. While not ruling out a natural spillover, the Republican staffers concluded that a “research-related incident” was the “most likely” origin.

Now House Republicans, newly in charge of their chamber, have opened a fresh probe of covid’s origin.