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Inside story of how one scientist came to the conclusion that COVID started from spreading in the wet Wuhan market

“The punishment for offenders can be harsh,” said Zhou Zhaomin, a political expert on the China wildlife trade at China Western 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 large quantities could result in life in prison.

But the enforcement of the laws was bad. Several researchers told MIT Technology Review that the illegal wildlife trade in China is “no secret.”

Indeed, Zhou and his colleagues conducted survey Between 2017 and 2019, it was discovered that a total of nearly 48,000 wild animals of 38 species were sold in four markets in Wuhan, including Huanan, almost all of which were sold alive, caged and stacked in cramped unsanitary conditions. ideal for transmitting the virus. Animals – wild-caught or farmed non-domesticated species – include species susceptible to SARS-CoV-1 and SARS-CoV-2, such as civets, minks, badgers, and raccoon dogs.

This study, published in June at Scientific reportsfound that all wildlife trade surveyed by the researchers was illegal. Many vendors sold protected species; none of them posted the required certifications to indicate the source of the animals or that they are not sick.

This means that once Huanan is implicated in the early cases of COVID-19, sellers selling live mammals are likely to illegally flee to avoid jail time, while law enforcement agencies are unlikely to admit at all that such an activity ever existed. With this in mind, it’s no surprise that the Chinese authorities have found no news of live animals being sold in the Huanan market, says Harvard’s Hanage.

After SARS, restrictions on wildlife trade were minimal, giving scientists virtually unlimited access to animals and traders in Guangdong’s wet markets, but even that wasn’t enough to help them pinpoint the source of SARS. While they quickly discovered viruses in civets, badgers, and raccoon dogs that were more than 99% identical to SARS-CoV-1, subsequent studies did not reveal a wide spread of the virus either in the wild or in agricultural conditions. The dominant view is that civets contracted the virus while tradingmost likely from bats that were bought and sold at the same time.

Now, 18 years later, the situation is strikingly similar. It seems to be no widespread circulation of SARS-CoV-2 in animals… None of the 80,000 or so samples tested by the Chinese team of the World Health Organization’s mission to find the sources of the pandemic, including prime suspects such as pangolins, civets, badgers and bamboo rats, contained the virus.

However, many scientists are still leaning towards the theory that wet markets played a critical role in the launch of COVID-19. While all eyes are on Yunnan and other parts of Southeast Asia as the most likely origin of the pandemic, Hanage says it is “not crazy” to speculate that Wuhan Hubei may have been where SARS-CoV-2 originated. naturally.

Indeed, scientists from the Wuhan Institute of Virology have found: SARS-like coronaviruses in bats in Hubei province… Despite the fact that they did not conduct systematic testing of farm animals for coronavirus infection throughout the province, in little-known study they found that all seven civets tested on a farm in the province in 2004 were infected with SARS-CoV-1 relatives. Several research groups in China and the United States are trying to figure out where the virus came from in animals, whether coronavirus infection among civets is more common than previously thought, and what impact this might have on our understanding of the origins of COVID-19.

Constant overflow

But without proof that the animal is infected with the coronavirus, which is more than 99% identical to SARS-CoV-2, some scientists continue to oppose natural origin.

One such critic is Alina Chan, a molecular biologist at the Broad Institute at MIT and Harvard (this publication is owned by but editorially independent of MIT). The main question, she said in recent webinar hosted by Science magazineThus, the virus entered Wuhan from caves more than a thousand miles away in China or other parts of Southeast Asia. “There is a very strong channel in Wuhan for scientists to descend to the places where they [knew] they will find the SARS viruses and deliver them to Wuhan city thousands of miles away, ”she said. However, there is no evidence of such routes for the wildlife trade, she adds.

This lack of clarity is also affecting the origin of SARS, says Linfa Wang, director of the Emerging Infectious Diseases Program at Duke National University of Singapore. The cave in which the closest relative of the bats SARS-CoV-1 was found is nearly 1,000 miles from the Guangdong market, where the first SARS cases were reported – similar to the distance between Wuhan and the site of one of the closest relatives of the SARS-CoV bats. … -2 was discovered.

And it is becoming increasingly clear that people in close contact with wildlife are becoming infected with coronaviruses much more often than previously thought.

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

Michael Sparrow

Research shows that up to 4% people who live near bats and work closely with wildlife in southern China have been infected with deadly animal-borne viruses, including coronaviruses. Laos and French team discovering close relatives of SARS-CoV-2, I learned that one in five bat handlers in Laos had antibodies against these coronaviruses.

Most of these secondary infections go away on their own, researchers say. In a study published in the journal Science in April, Warobi and colleagues show through computer simulations that urban conditions are critical to the spread of SARS-CoV-2, which can cause major epidemics – without it, it will die out very quickly.

“It is hundreds, if not thousands, times more likely” that a wildlife trader who encountered the predecessor of SARS-CoV-2 – either from bats or another animal species – brought the infection to Huanan than that explorer. who went to collect samples from the bats, they returned to Wuhan with the pathogen and then brought it to Huanan, Wang says.

Sparrow agrees. Based on ample evidence, he is now convinced not only that the pandemic’s connection to the Huanan market is real, but that this is where the ancestor of SARS-CoV-2 passed from animal to human. “This is much more likely than any other scenario based on what we now know,” he says.

He adds that preliminary findings from the ongoing work of his group and others will help reinforce the “They’re all pointing in the same direction” argument.

This article was supported by a grant from the Pulitzer Center.


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