Scientists Press Case Against the Covid Lab Leak Theory

In the latest volley of the debate over the origins of the coronavirus, a group of scientists this week presented a review of scientific findings that they argue shows a natural spillover from animal to human is a far more likely cause of the pandemic than a laboratory incident.

Among other things, the scientists point to a recent report showing that markets in Wuhan, China, had sold live animals susceptible to the virus, including palm civets and raccoon dogs, in the two years before the pandemic began. They observed the striking similarity that Covid-19’s emergence had to other viral diseases that arose through natural spillovers, and pointed to a variety of newly discovered viruses in animals that are closely related to the one that caused the new pandemic.

The back and forth among scientists is taking place while intelligence agencies are working with an end-of-summer deadline to provide President Biden with an assessment of the origin of the pandemic. There is now a division among intelligence officials as to which scenario for viral origin is more likely.

The new paper, which was posted online on Wednesday but has yet to be published in a scientific journal, was written by a team of 21 virologists. Four of them also collaborated on a 2020 paper in Nature Medicine that largely dismissed the possibility that the virus became a human pathogen through laboratory manipulation.

One of the signers of the May 2021 letter, Michael Worobey of the University of Arizona, became a co-author of the new paper arguing for a natural spillover.

He said his views have evolved as more information emerges. Among other reasons for Dr. Worobey’s shift was the growing evidence about the Huanan animal market in Wuhan. When the pandemic first arose in Wuhan, Chinese officials tested hundreds of samples from animals sold at the market and did not find the coronavirus in any of them.

But last month a team of researchers presented an inventory of 47,381 animals from 38 species sold in Wuhan markets between May 2017 and November 2019. It included species like civets and raccoon dogs that can act as intermediate hosts for coronaviruses.

Dr. Worobey called that study “a game-changing paper.”

He also pointed to the timing of the earliest cases of Covid in Wuhan. “The Huanan market is right at the epicenter of the outbreak, with later cases then radiating outward in space from there,” Dr. Worobey said in an email.

“No early cases cluster anywhere near the W.I.V., which has been the focus of most speculation about a possible lab escape,” he said.

Other scientists, however, say that such arguments are speculative, and that the new review is mostly a rehash of what was already known.

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