Two new studies provide further evidence that the coronavirus pandemic originated in a market in Wuhan, China, where live animals were sold, further bolstering the theory that the virus emerged in nature rather than escaping from a Chinese laboratory.
The research, published online Tuesday by the journal Science, shows that the wholesale seafood market in Huanan was likely the early epicenter of the scourge that has now killed nearly 6.4 million people worldwide. Scientists conclude that the virus that causes COVID-19, SARS-CoV-2, likely spilled from animals to people on two separate occasions.
“All this evidence tells us the same thing: It points directly 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 a co-author of one of the studies. “I was pretty convinced about the leak from the lab until we got into it very carefully and looked at it a lot more closely.” FILE – Residents line up to be tested for COVID-19 in Wuhan, central China’s Hubei province on August 3, 2021 Two new studies provide further evidence that the coronavirus pandemic originated in a market in Wuhan, China where live animals were being sold, further bolstering the theory that the virus emerged in nature rather than escaping from a Chinese laboratory. The research was published online Tuesday, July 26, 2022, by the journal Science. (Chinatopix via AP, File)
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 first cases of COVID-19 reported since 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.
They asked, “Of all the places where the first cases could have lived, where did they live? And it turned out that when we were able to look at it, there was an extraordinary pattern where the highest density of cases was very close and very focused on that market,” Worobey said at a press conference. “Crucially, this applies to all cases in December as well as cases with no known link to the market… And this is an indication that the virus started to spread among people working in the market but then started to spread to the local community.”
Andersen said they also found clusters of cases within the market, “and that clustering is very, very specifically in the parts of the market” where they now know people were selling wildlife, such as raccoon dogs, susceptible to coronavirus infection . .
In the other study, the scientists analyzed the genomic diversity of the virus inside and outside of China, starting with the first sampled genomes in December 2019 and extending to mid-February 2020. They found that two lineages , A and B, marked the beginning of the pandemic in Wuhan. Study co-author Joel Wertheim, an expert in viral evolution at the University of California, San Diego, noted that the A lineage is more genetically similar to bat coronaviruses, but the B lineage appears to have started to spread before in humans, especially in the market.
“I realize now that it sounds like he just said that a once-in-a-generation event happened twice in short succession,” Wertheim said. But there were certain conditions, such as people and animals in close proximity and a virus that can spread from animals to people and from person to person. Therefore, “the barriers to spread have been reduced so that we think multiple introductions should really be expected,” he said.
Many scientists believe that the virus jumped from bats to humans, either directly or through another animal. But in June, the World Health Organization recommended a deeper investigation into whether a lab accident could be to blame. Critics had said the WHO was too quick to dismiss the lab leak theory.
“Have we disproved the lab leak theory? No, we haven’t,” Andersen said. “But I think what’s really important here is that there are possible scenarios and there are plausible scenarios and it’s very important to understand that possible doesn’t mean equally likely.”
The origins of the pandemic remain controversial. Some scientists believe a lab leak is more likely and others remain open to both possibilities. But Matthew Aliota, a researcher at the University of Minnesota College of Veterinary Medicine, said in his opinion that the pair of studies “hopefully puts the lab leak hypothesis to rest.”
“These two studies really provide compelling evidence for the natural origin hypothesis,” said Aliota, who was not involved in either study. Because it’s impossible to sample an animal that was on the market, “it’s probably as close to a smoking gun as you could get.”
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