The inside story of how a scientist ended up covid starting a spillover in the Wuhan wet market


“The penalties for offenders can be harsh,” said Zhou Zhaomin, an expert on China’s wildlife trade policy at China West Normal University in Nanchong. Those who trade in protected species could face up to 15 years in prison, and smuggling them into or out of China in sufficient quantities could result in a life sentence.

But law enforcement is not good. Several researchers told the MIT Technology Review that it was “an open secret” that illegal wildlife trafficking is widespread in China.

In fact, Zhou and his teammates performed a survey between 2017 and 2019 found that four markets in Wuhan, including Huanan, sold a combined total of nearly 48,000 wild animals of 38 species, almost all of which were sold live , confined, and placed in cramped, unsanitary conditions ideal for virus transmission. Animals — even wild-caught or cultivated homeless species — include species vulnerable to SARS-CoV-1 and SARS-CoV-2, such as civets, mink, badgers, and raccoon dogs. .

That study, published in June on Scientific reports, found that all wildlife businesses surveyed by the researchers were illegal. Many vendors sell protected species; no one posted the required certificates indicating the source of the animals or that they were free of diseases.

This means that when Huanan was involved in early covid-19 cases, traffickers who sold live mammals, likely illegally, would flee to avoid facing imprisonment, while law enforcement agencies is unlikely to admit such activities existed before. Given this, it is not surprising that Chinese authorities have found no leads regarding the sale of live animals in the Huanan market, says Hanage of Harvard.

Wildlife trade bans came little after SARS, giving scientists almost unlimited access to animals and traders in Guangdong’s wet markets — but even that wasn’t enough to help them figure it out. the origin of SARS. While they can easily get viruses in civet, badger, and raccoon dogs more than 99% identical to SARS-CoV-1, subsequent investigations did not show widespread circulation of the virus, either in the wild or in farm conditions. A dominant view is that Civets caught the virus during trading, probably from bats bought and sold at the same time.

Now, 18 years later, the situation is much the same. Murag naay there is no widespread circulation of SARS-CoV-2 in animals. None of the 80,000 or more samples tested by the Chinese team on the World Health Organization mission to find the sources of the pandemic — including key suspects such as pangolins, civets, badgers, and bamboo rats — contained the virus. .

However, many scientists still rely on the theory that wet markets play an important role in triggering covid-19. Even if all eyes are on Yunnan and other parts of Southeast Asia as the most likely areas of pandemic origin, Hanage said it was “not batshit crazy” to suggest that Hubei province of Wuhan may be where SARS-CoV-2 naturally arises.

In fact, scientists at the Wuhan Institute of Virology found Coronaviruses such as SARS in Hubei bats. Even if they have not yet systematically tested farm animals for coronavirus infection across the province, in a little known study conducted after SARS, they found that seven civets they tested on a provincial farm in 2004 were purely infected with SARS-CoV-1 relatives. Many research teams in China and the U.S. are trying to find out where the virus is acquired in animals, whether coronavirus infection in civets is more common than previously thought, and what effect it might have on our understanding the origin of covid-19.

Frequent spillover

But in the absence of evidence of an animal infected with a coronavirus that is more than 99% identical to SARS-CoV-2, some scientists continue to argue against the natural origin.

One such critic is Alina Chan, a molecular biologist at the Broad Institute at MIT and Harvard (this publication is owned by MIT, but editorially independent of it). The central question, he says in a recent webinar organized by Science magazine, is the way the virus reached Wuhan from caves more than a thousand miles away in China or other parts of Southeast Asia. “There is a very fast flow of scientists in Wuhan going to the places where they are [knew] they can find the SARS viruses, which carry them as far as Wuhan town, like thousands of miles away, ”he said. There is no evidence, however, of such routes for wildlife trade, he added.

Such a lack of explanation also plagues the origins of SARS, said Linfa Wang, director of the emerging infectious diseases program at Duke-National University Singapore. The cave that provides the closest bat relative to SARS-CoV-1 is nearly 1,000 miles away from the Guangdong market where the first SARS cases appeared — similar to the distance between Wuhan and in the area where one of the bat’s closest relatives of SARS -CoV -2 was discovered.

And it’s even more obvious that people in close contact with wildlife are infected with coronaviruses more often than previously thought.

“[Huanan] more likely than in other scenarios based on what we know now. “

Michael Worobey

Studies have shown that up to 4% of people living near bats and working closely with wildlife in southern China is infected with deadly animal -borne viruses, including coronaviruses. A Laotian and French team, who discovered the closest relative of SARS-CoV-2, found to be One in five bat handlers in Laos has antibodies against coronaviruses.

Most spillover infections are eradicated on their own accord, the researchers said. In a study published in Science in April, Worobey and his colleagues showed in a computer simulation that for the spillover of SARS-CoV-2 to cause major epidemics, an urban situation is critical-without that, it could easily die.

“Hundreds, if not thousands, more likely” that a wildlife trader exposed to a progenitor of SARS-CoV-2-from bats or other animal species-brought Huanan infection than a researcher went. to collect samples from the bats returned to Wuhan with the pathogen and then brought them to Huanan, according to Wang.

Worobey agreed. Based on multiple lines of evidence, he is now convinced not only that the pandemic connection to the Huanan market is real, but where a progenitor of SARS-CoV-2 jumped from an animal to humans. “That’s a bigger possibility than any other scenario based on what we know now,” he said.

Preliminary results from the ongoing work of his team and others will help further strengthen the case, he added: “They are all pointing in the same direction.”

Reporting for this article was supported by a grant from the Pulitzer Center.



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