Two new studies provide more evidence that the coronavirus pandemic originated in Wuhan, the China market where live animals were sold — bolstering the theory that the virus emerged in the wild rather than escaping from a Chinese laboratory.
The research, which was published online by Science magazine on Tuesday, showed that the Huanan Seafood Wholesale Market was likely the first center of the epidemic that has so far claimed nearly 6.4 million lives worldwide. Scientists have concluded that the virus that causes COVID-19, SARS-CoV-2, likely passed from animals to humans two separate times.
“All this evidence tells us the same thing: It points directly to this particular market in central 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 completely convinced of the lab leak myself until we delved into this very carefully and looked at it more closely.”
In one studywhich included data collected by Chinese scientists, University of Arizona evolutionary biologist Michael Worby and colleagues used mapping tools to estimate the locations of more than 150 of the first reported COVID-19 cases as of December 2019. They also identified cases from January and February 2020 using data from a social media app that created a channel for people with COVID-19 to get help.
They asked, “Of all the locations where the early cases would have lived, where did they live? And it turns out that when we were able to look at this, there was this extraordinary pattern where the highest density of cases was very close to and very concentrated in this market,” Worobey said at a press conference. “Crucially, this applies to both the cases in December and also to cases with no known connection to the market… This is an indication that the virus started spreading in people who worked in the market but then started spreading in the local community.”
Andersen said they’ve found clusters of cases within the market as well, “and this conglomeration is very specifically in parts of the market” where they now know that people are selling wild animals, like raccoon dogs, that are susceptible to infection with the coronavirus. .
In the other studyIn the study, scientists analyzed the genetic diversity of the virus within and outside China starting with the closest genome sample in December 2019 and extending through mid-February 2020. They found that two strains – A and B – marked the beginning of the epidemic in Wuhan. Study co-author Joel Werthem, an expert in viral evolution at the University of California, San Diego, noted that strain A is more genetically similar to bat coronaviruses, but it appears that strain B began spreading earlier in humans, particularly in the market.
“Now I realize it’s as if I just said a once-in-a-generation event happens twice in short succession,” Werthem said. But there were certain circumstances – such as having people and animals in close proximity and a virus that can be transmitted from animals to humans and from person to person. Therefore, “the barriers to indirect propagation have been lowered so that multiple precursors can be expected, we think, in effect,” he said.
Many scientists believe that the virus jumped from bats to humansEither directly or through another animal. But in JuneThe World Health Organization has recommended a deeper investigation to find out if the laboratory accident was the cause. Critics said the WHO was too quick to dismiss the lab leak theory.
“Did we disprove the lab leak theory? No, we didn’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 really important to understand that possible doesn’t mean equal probability.”
The origins of the pandemic remain controversial. Some scientists believe that the possibility of a leak in the lab 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 mind that these two studies “kind of calm, hopefully, the lab leak hypothesis.”
“These two studies really provide convincing evidence for the hypothesis of natural origin,” said Aliota, who was not involved in either study. Since sampling an animal that was on the market is impossible, “this is probably as close to a smoke gun as you can get.”
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