“There is a very, very strong case that the Huanan market was indeed the epicenter,” said one of the researchers.
Two landmark studies investigating the origins of the COVID-19 pandemic have concluded that there is overwhelming evidence that the SARS-CoV-2 virus spilled from animals to humans at a live animal market in Wuhan, China.
Both studies, published in the journal Science Tuesday, were conducted by large teams that included some of the world’s highest-profile virologists and disease modelers.
This includes Michael Worobey, a Canadian evolutionary biologist who heads the Department of Ecology and Evolutionary Biology at the University of Arizona, and has been a leading scientific voice calling for deeper research into the origins of the COVID-19 pandemic. .
“There is a very, very strong case that the Huanan market was indeed the epicenter,” Worobey said shortly after it was published on Tuesday.
The studies refute theories that the virus may have originated in a Chinese lab, which has spread widely on the Internet and gained traction among some politicians.
One of the studies looked at how some of the early cases of COVID-19 clustered around Wuhan’s Huanan wholesale seafood market; the other, delved into the genetic history of the virus, noting when and how it made the jump from animals to humans.
In the first study, led by Worobey with a team of 19 scientists from the United States, Canada, the Netherlands, the United Kingdom, Belgium and Australia, the researchers drew on data collected from a World Health Organization mission (WHO) that investigated the origins of the disease. virus
Published in March 2021, the WHO study showed that 55 of the first 168 known cases of COVID-19 were associated with the market. But that was not enough to establish that Huanan Seafood Wholesale Market in Wuhan was the epicenter of the pandemic.
Two months later, Worobey — who is well-known for investigating the origins of diseases such as HIV and the 1918 Spanish flu — was among a handful of scientists who signed a letter calling on researchers to take seriously “natural overflows and laboratory until we have enough data.”
Pushed by former US President Donald Trump and a handful of conservative US politicians, the theory that the SARS-CoV-2 virus originated in a laboratory in Wuhan was revived after The Wall Street Journal published details of ‘a classified report from a US government laboratory that he found was plausible and merited further investigation.
Where did the first cases live?
The data Worobey and his colleagues pulled from the WHO report represented the first known cases of the virus in Wuhan, a city of roughly 11 million people.
But the WHO report did not specify the exact coordinates of each patient’s home. So the researchers overlaid the maps to identify the exact latitude and longitude of each patient.
To find more cases radiating from the market, the researchers layered social media “log” data from a Weibo channel created for people with COVID-19 to seek medical help.
With this information, the team could ask the question: Across the 8,000 square kilometers of greater Wuhan where the first cases might have emerged, where did they live?
“There was this extraordinary pattern where the highest density of cases was very close and very concentrated in this market,” Worobey said. “It was a very, very small area, about a third of a square kilometer, with Huanan Market in the middle.”
Worobey said that even when they removed two-thirds of the cases closest to the market, the results still showed a connection to the market that could not be explained by chance.
Many of the infected people lived near the market, but never had contact with it.
Worobey pointed to a chain of transmission where infected market vendors entered local shops, infecting workers and customers before spreading to a wider population not linked to the market.
The density of the city and its connections to the world was the initial fuel that allowed the pandemic to burn in recent years, added the Canadian researcher who used to work as a firefighter in B.C.
“You drop the same virus in a rural environment, it just runs out 99 percent of the time. You drop it in a big city like Wuhan and then it takes off.”
The virus probably jumped to humans twice
In the second study in Science, the researchers found that there were at least two transmission events between species other than humans.
By analyzing the “molecular clock” of the virus strains and then running several simulations, the researchers found that there were probably eight, but possibly as many as two dozen introductions of SARS-CoV-2 prior to its transmission successful in Wuhan market.
The first successful overflow likely occurred around November 18, 2019, while the second overflow likely occurred “within a few weeks even,” according to the study led by Jonathan Pekar of the Department of Biomedical Informatics at the University of California at San Diego.
The group found that it was highly unlikely that SARS-CoV-2 was circulating widely in humans before November 2019.
Kristian Andersen, co-author of the Worobey study and a researcher in the Department of Immunology and Microbiology at The Scripps Research Institute, said multiple spillovers of the virus in the human population are not unusual.
In fact, that’s exactly what happened in 2002 and 2003, when SARS-CoV-1 spilled into humans through the wildlife trade, wet markets and restaurants that sold infected animals, he said.
“I was pretty convinced of the lab leak myself,” Andersen said, “until we got into it very carefully and looked at it much more closely.”
Going through a “lab leak”
Worobey’s study also looked at the market, analyzing environmental samples collected by Chinese scientists in early 2020.
The researchers found that the sale of wild animals, such as raccoon dogs, badgers, deer and bamboo rats, was clustered in several specific areas of the market where positive virus samples were found in cages and meat cellars.
“There are many other animals that could have brought this particular virus into this market that were infected with this virus,” Andersen said. “We don’t really have clarity on that.”
“It’s one of those key questions that is absolutely critical.”
That’s because understanding where infected animals come from could help scientists understand how these zoonotic viruses behave and might spread again in the future.
Whether on a farm or in the wild, figuring out what happened before the virus hit the market would also give researchers involved in virus surveillance a place to start looking, says Angela Rasmussen, another co-author and virologist for Vaccines and Disease infectious Organization at the University of Saskatchewan.
“That’s really what’s needed to move past this whole discussion of ‘Did it come from nature? Did it come from a lab?'” Rasmussen said.
Instead, he says it raises other really important questions, such as: What is the risk of a new coronavirus linked through the animal trade re-emerging in people?
“All we know is that the animals were brought to the market through a common supply chain and we know what species of animals were in the market, but we currently have no data to show which of those species were infected Rasmussen said. .
Some of that data might still exist somewhere in China, Worobey said. But accessing it will require international collaboration with Chinese scientists, which Andersen and Rasmussen say has been cut off in many cases due to political pressure.
Worobey added that Chinese officials were not fans of either the lab leak theory or the evidence that it spread from the Wuhan market.
Chinese scientists, on the other hand, are big fans of the truth, like any scientist, Worobey said.
“It’s bloody lucky that the doctors at Xinhua Hospital were so alert that they noticed these cases as something unusual at the end of December,” Worobey added. “The Chinese data … has been absolutely crucial to getting to the truth.”
Although not complete, the evidence the researchers got their hands on is among the best datasets of the early onset of a global pandemic ever recorded.
What people need to realize, Rasmussen says, “is that taking all these different incomplete data sets and following the lines of evidence where they lead us, they all lead us to the same point … there are no other alternative explanations. .”
International surveillance is not keeping pace with a changing world
While scientific cooperation with Chinese researchers has largely broken down compared to the start of the pandemic, international surveillance of emerging zoonotic viruses has also stumbled, say researchers involved in the two studies.
“I actually don’t think we’re any better off than we were at the beginning of the pandemic because, again, we minimize the risk of these infectious diseases, we don’t really collaborate,” Andersen said.
“We need transparency and data reporting. We need to have prompt reporting and cooperation. We need to have very strong surveillance systems.”
And then there’s the funding, Rasmussen says, which underpins the entire effort to catch emerging diseases before they erupt into a pandemic.
“There are still a lot of holes around the world,” he said, noting the emergence of monkeypox. “We’re not making these investments because they don’t affect the people of Canada, they don’t affect the people of the US, they don’t affect the people of Europe, until they do.”
This is especially important now because the possibility for humans to interact with animals increases every year. Climate change and ever-changing land use patterns are…