Two new studies provide more evidence that the coronavirus pandemic originated in the Chinese city of Wuhan, where live animals were sold – further bolstering the theory that the virus originated in the wild rather than escaping a Chinese laboratory.
The study, published online Tuesday in the journal Science, suggests that the Huanan seafood wholesale market was the initial epicenter of the outbreak, which has killed an estimated 6.4 million people worldwide. Scientists have concluded that the virus that causes COVID-19, SARS-CoV-2, spilled from animals to humans on two separate occasions.
“All of this evidence tells us the same thing: it points to this market in the middle of Wuhan,” said Christian Andersen, professor of immunology and microbiology at Scripps Research and one of the study’s authors. “I’m pretty sure there’s a lab leak, and we’ve gone into it carefully and looked into it closely.”
In one studyThe Chinese scientists, including University of Arizona evolutionary biologist Michael Urobei and his team, used mapping tools to estimate the location of more than 150 of the earliest reported cases of COVID-19 since December 2019. They also mapped the cases for 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 places where the first people lived, where did they live? When we looked at it, it became clear that there is an amazing pattern with the highest density of activity very close to this market and very centralized, “said Vorobey in a press briefing. … This is an indication that the virus spread among people working in the market, but then spread to the local community.”
According to Andersen, they also found clusters within the market, “and cluster-specific parts of the market,” where they now know people are selling wild animals that have been exposed to the coronavirus, such as raccoon dogs. .
In another 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 – started the pandemic in Wuhan. Study author Joel Wertheim, an expert on viral evolution at the University of California, San Diego, noted that the A strain is genetically similar to bat coronaviruses, but the B strain began to spread earlier in humans, especially in the marketplace.
“Now I understand that it seems like a once-in-a-generation event has happened twice in a short amount of time,” Wertheim said. But there were certain conditions – for example, people and animals in close proximity and the virus being transmitted from animals to humans and from humans to humans. Thus, “barriers to proliferation have been lowered, so multiple introductions are to be expected,” he said.
Many scientists believe that the virus passed from bats to humans, directly or through another animal. But in June, the World Health Organization recommended a deeper investigation into whether a lab accident was to blame. Critics 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 the bottom line here is that there are possible scenarios and plausible scenarios and that doesn’t mean possible.”
The origin of the pandemic remains controversial. Some scientists believe a lab leak is more likely, while others remain open to both possibilities. But Matthew Aliota, a researcher at the University of Minnesota’s College of Veterinary Medicine, said he thinks the pair of studies “hopefully puts the laboratory leak hypothesis to rest.”
“Both of these studies provide compelling evidence for the natural origin hypothesis,” said Aliota, who was not involved in either study. “It’s probably as close to a smoking gun as you can get,” since it’s impossible to sample a marketed animal.
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