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 originated in the wild rather than escaping from the wild. a Chinese laboratory.
The research, published online Tuesday by the journal Science, shows the Huanan Seafood Wholesale Market was likely the first epicenter of the plague that has now killed nearly 6.4 million people worldwide. Scientists conclude that the virus that causes COVID-19, SARS-CoV-2, likely spread from animals to humans twice.
“All of 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 co-author of one of the studies. . “I myself was pretty convinced of the leak from the lab until we looked at it very carefully and looked at it more closely.”
In a 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 cases of COVID-19. reported 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.
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 that, there was this extraordinary pattern where the highest case density was both extremely close and very centered in that market,” Worobey said during a briefing. hurry. “Basically, this applies to both all cases in December and also cases with no known link to the market… And this indicates that the virus started to spread among people who worked in the market but then started to spread. spread in the local community. ”
Andersen said they also found clusters of cases inside the market, “and the clustering is very, very specific in parts of the market” where they now know people were selling wild animals, such as raccoon dogs, which are susceptible to coronavirus infection.
In the other study, the scientists analyzed the genomic diversity of the virus inside and outside China starting with the first genome samples in December 2019 and up to mid-February 2020. They have discovered that two lineages – A and B – marked the start of the pandemic in Wuhan. Study co-author 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 started to spread earlier in humans, especially in the market.
“Now I realize it looks like I just said a once-in-a-generation event happened twice in a row,” Wertheim said. But certain conditions were in place – like people and animals in close proximity and a virus that can spread from animals to people and from person to person. Thus, “the barriers to spinoffs have been lowered so that multiple introductions, in our view, should in fact be expected,” he said.
Many scientists believe the virus jumped from bats to humans, either directly or through another animal. But in June, the World Health Organization recommended further investigation to determine whether a lab accident might 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 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 also likely.”
The origins of the pandemic remain controversial. Some scientists think 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 hopefully end 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 at the market, “that might be as close to a gun smoker as you could get.”