Despite the resurgence of the lab-leak theory, there is mounting evidence that COVID-19 jumped to humans from a wild animal illegally sold at a meat market, not from a Chinese research facility, says a prominent University of Arizona researcher who specializes in the origins of outbreaks.
Evolutionary biologist Michael Worobey now says transmission from another species is the most likely scenario by a wide margin, based on recent analysis of early infections and other data that points to one particular market near the center of Wuhan.
“It’s very likely that what happened is the same thing that happened with the first SARS outbreak in 2002-2003: crossover from wildlife being illegally sold at a market in China,” Worobey said Thursday.
The latest findings come just two months after he and 17 other top scientists from the U.S., Canada and Europe called for more study of the lab-leak theory.
Their letter, published in the journal Science, said the outbreak could still be the result of an accidental release from a lab, but that possibility had not been given “balanced consideration” so far. “We must take hypotheses about both natural and laboratory spillovers seriously until we have sufficient data,” the May 14 letter stated.
Worobey said his thinking on that hasn’t changed.
“I always thought that the lab leak was a long shot, but I thought it was worth investigating. I did then, and I do now,” he said.
But that possibility seems even more remote based on a new summary by Worobey and others that lays out the case for so-called “zoonotic spillover” from the Huanan Seafood Wholesale Market.
One key revelation, he said, is a recent report by a team of wildlife biologists debunking claims by Chinese authorities that no illegal animal trade occurred at the Huanan market. Instead, the biologists found evidence of sales involving raccoon dogs and palm civets, two Asian mammals linked to previous crossover outbreaks in humans.
The paper by Worobey and 20 other researchers was posted July 7 on the website Zenodo, an open scientific repository where researchers can easily upload their data for others to read and analyze. Throughout the pandemic, scientists have been using such open-access sites to quickly share their findings to aid the global fight against the virus.
As a viral detective of sorts, Worobey, the head of UA’s Department of Ecology and Evolutionary Biology, has previously traced the origins of the HIV/AIDS epidemic and the 1918 influenza pandemic, but his focus these days is squarely on the coronavirus.
Last year, he co-authored a study showing that the earliest widespread outbreak of COVID-19 in the U.S. was most likely triggered by a patient who arrived from China almost a month later than previously thought — and roughly two weeks after then-President Trump restricted travel from that country.
Then in March, Worobey and his fellow researchers released findings that suggest the coronavirus was circulating undetected in China for up to two months before the first human cases were reported in Wuhan in late December 2019.
Worobey said he is “a bit dismayed” by the complete politicization of COVID-19, from the fight over masks and vaccines to the investigation into the origins of the virus.
He knew he was sticking his neck out by signing onto the letter published in Science, but he hoped it would give researchers some cover to continue exploring every possible explanation — no matter how unlikely or unpopular — for how the pandemic began.
Shortly after the letter came out, though, the Biden administration announced a renewed push to investigate the lab-leak theory, angering the Chinese government and dimming the prospects for unfettered scientific cooperation between the two countries.
Worobey said he doesn’t regret signing it, but “it’s possible the letter actually backfired in that sense.”
“We may have lost an opportunity to engage with scientists (in China) who are now feeling defensive,” he said.
Even so, Worobey remains hopeful that the definitive cause of COVID-19 will be found someday, though he worries that Chinese secrecy, international tensions and partisan wrangling at home are delaying that work.
The colder the case becomes, the harder it will be to solve, he said, so scientists must ignore the politics and press on.
“We’re now more than a year and a half out from when this pandemic started,” Worobey said. “I’m not completely ignorant of the political contours of this, but as a scientist, you have to try to just let the chips fall where they may.”