The research, published online Tuesday by the journal Science, shows that the Huanan Seafood Wholesale Market was likely the early epicenter of the scourge that has now killed nearly 6.4 million people around the world. Scientists conclude that the virus that causes COVID-19, SARS-CoV-2, likely spilled from animals into people two separate times.
“All this evidence tells us the same thing: It points right to this particular market in the middle of Wuhan,” said Kristian Andersen a professor in the Department of Immunology and Microbiology at Scripps Research and co-author of one of the studies. “I was quite convinced of the lab leak myself until we dove into this very carefully and looked at it much closer.”
In one study, which incorporated data collected by Chinese scientists, University of Arizona evolutionary biologist Michael Worobey and his colleagues used mapping tools to estimate the locations of more than 150 of the earliest reported COVID-19 cases from December 2019. They also mapped cases from January and February 2020 using data from a social media app that had created a channel for people with COVID-19 to get help.
In the other study, scientists analyzed the genomic diversity of the virus inside and outside of China starting with the earliest sample genomes in December 2019 and extending through mid-February 2020. They found that two lineages – A and B – marked the pandemic’s beginning in Wuhan. Study coauthor Joel Wertheim, a viral evolution expert at the University of California, San Diego, pointed out that lineage A is more genetically similar to bat coronaviruses, but lineage B appears to have begun spreading earlier in humans, particularly at the market.
“Now I realize it sounds like I just said that a once-in-a-generation event happened twice in short succession,” Wertheim said. But certain conditions were in place — such as people and animals in close proximity and a virus that can spread from animals to people and from person to person. So “barriers to spillover have been lowered such that multiple introductions, we believe, should actually be expected,” he said.
“Have we disproven the lab leak theory? No, we have not,” Andersen said. “But I think what’s really important here is there are possible scenarios and there are plausible scenarios and it’s really important to understand that possible does not mean equally likely.”
Matthew Aliota, a researcher in the college of veterinary medicine at the University of Minnesota, said in his mind the pair of studies “kind of puts to rest, hopefully, the lab leak hypothesis”.
“Both of these two studies really provide compelling evidence for the natural origin hypothesis,” said Dr Aliota, who was not involved in either study.
He said sampling an animal that was at the market at the time was now impossible.
“This is maybe as close to a smoking gun as you could get,” he added.