By LAURA UNGAR, AP Science journalist
Two new studies provide more evidence that the coronavirus pandemic originated in a market in Wuhan, China, where live animals were sold, further bolstering the theory that the virus arose in the wild rather than escaping from a laboratory. Chinese.
The research, published online Tuesday by the journal Science, shows that the Huanan wholesale seafood market 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 passed from animals to people on two separate occasions.
“All of this evidence tells us the same thing: It points squarely at 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 of the lab leak until we dove into this very carefully and took a much closer look at it.”
In one study, which incorporated data collected by Chinese scientists, University of Arizona evolutionary biologist Michael Worobey and colleagues used mapping tools to estimate the locations of more than 150 of the first reported COVID-19 cases 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.
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They asked, “Of all the places the first cases might have lived, where did they live? And it turned out that when we were able to see this, there was an extraordinary pattern where the highest density of cases was extremely close to and very focused on this market,” Worobey told a news conference. “Crucially, this applies both to all cases in December and to cases with no known link to the market… And this is an indication that the virus started to spread in people who worked in the market but then it began to spread to the local community. ”
Andersen said they also found clusters of cases within the market, “and that clustering is very, very specific to the parts of the market” where they now know people were selling wildlife, like raccoon dogs, that are susceptible to coronavirus infection. . .
In the other study, scientists analyzed the genomic diversity of the virus inside and outside of China, starting with the first sample genomes in December 2019 and extending through 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 lineage A is most genetically similar to bat coronaviruses, but lineage B appears to have started spreading earlier in humans, particularly in the market.
“I realize now that it sounds like I just said a once-in-a-generation event happened twice in a row,” 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. So “the barriers to spillover have been lowered, so we think you should really expect multiple introductions,” he said.
Many scientists believe that the virus passed from bats to humans, either directly or through another animal. But in June, the World Health Organization recommended further investigation into whether a lab accident may be to blame. Critics had said the WHO was 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 and 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’s School of Veterinary Medicine, said in his mind that the pair of studies “sort of puts to rest, hopefully, the lab leak hypothesis.”
“These two studies really provide compelling evidence for the natural origin hypothesis,” said Aliota, who was not involved in either study. Since it’s impossible to sample an animal that was on the market, “this is maybe as close to a weapon as you could get.”
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