TECHNOLOGY

The inside story of how a scientist wrapped up COVID began with an outbreak at the wet market in Wuhan


“Punishments can be harsh,” says Zhou Zhaomin, a policy expert on China’s wildlife trade at China West Normal University in Nanchong. Trading in protected species can face up to 15 years in prison, and smuggling them into or out of China in large enough numbers could result in life imprisonment.

But enforcement of the laws was weak. Several researchers have told MIT Technology Review that it is an “open secret” that illegal wildlife trade is rampant in China.

In fact, Zhou and colleagues conducted Questionnaire Between 2017 and 2019 it found that four markets in Wuhan, including Huanan, sold nearly 48,000 wild animals of 38 species, nearly all of which were sold live, caged, and stacked in cramped and unsanitary conditions ideal for transmission of the virus. Animals – whether wild-caught or non-domesticated – include species susceptible to both SARS-CoV-1 and SARS-CoV-2, such as civets, minks, badgers, and raccoon dogs.

That study, published in June in Scientific Reports, it was found that all of the wildlife trade the researchers included were illegal. Several sellers sold the protected species; None of them published the required certificates that indicated the animals were sourced or disease-free.

This means that once Huanan has been implicated in early covid-19 cases, sellers who sell live mammals, most likely illegally, will flee to avoid facing imprisonment, while law enforcement agencies are unlikely to admit that such activities existed in the first place. In light of this, it is not surprising that Chinese authorities have not found evidence regarding sales of live animals at the Huanan market, says Harvard’s Hanage.

Restrictions on the wildlife trade were minimal in the aftermath of SARS, giving scientists nearly 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 soon they hosted viruses in civets, badgers, and raccoon dogs which were so More than 99% identical to SARS-CoV-1Subsequent investigations did not result in a widespread spread of the virus, either in the wild or in farm conditions. The prevailing view is that Civet caught the virus while trading, most likely from bats that were bought and sold at the same time.

Now, 18 years later, the situation is strikingly similar. There seems to be There is no widespread circulation of SARS-CoV-2 in animals. None of the 80,000 or so samples tested by the Chinese team to the WHO mission to search for the origins of the epidemic — including prime suspects such as pangolins, civets, badgers and bamboo rats — contained the virus.

However, many scientists are still heavily inclined towards the theory that wet markets played a critical role in the launch of COVID-19. Although all eyes are on Yunnan and other parts of Southeast Asia as the most likely places for the origins of the epidemic, Hanage says it is “not crazy” to suggest that Hubei province in Wuhan could have been where SARS-CoV-2 emerged. Normally.

In fact, scientists at the Wuhan Institute of Virology found SARS-like coronaviruses in bats in Hubei. Although they did not systematically test farm animals for coronavirus infection across the county, in unknown study They were made in the aftermath of SARS, and they found that seven civets they tested on a county farm in 2004 were all infected with SARS-CoV-1 relatives. Several research teams in China and the United States are trying to find out where animals have contracted the virus, whether coronavirus infection among civets is more common than previously thought, and what impact this has on our understanding of the origins of COVID-19.

continuous spread

But without evidence that an animal has a coronavirus that is more than 99% identical to SARS-CoV-2, some scientists have continued to argue against the natural origins.

These critics include Alina Chan, a molecular biologist at MIT’s Broad Institute and Harvard (this publication is owned by, but editorially independent of, MIT). She said the central question in a A webinar organized recently by Science magazine, How the virus got to Wuhan from caves more than a thousand miles away in China or other parts of Southeast Asia. “There is a very strong channel of scientists in Wuhan coming down to these places where they are [knew] They will find SARS viruses, take them to Wuhan, like thousands of miles away.” She adds that there is no evidence, however, for such wildlife trade routes.

Such a lack of clarity also plagues the origins of SARS, says Linfa Wang, director of the Emerging Infectious Diseases Program at Duke National University in Singapore. The cave that yielded the closest relative of SARS-CoV-1 bats is about 1,000 miles from the Guangdong market where the first SARS cases appeared – similar to the distance between Wuhan and the location where one of the closest bat relatives of SARS-CoV-2 was discovered.

It is increasingly clear that people in close contact with wildlife are infected with coronaviruses more frequently than previously thought.

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

Michael Worby

Studies show that up to 4% of People who live near bats And Working closely with wildlife In southern China, deadly animal-borne viruses, including coronaviruses, have been found. Laotian and French team discover SARS-CoV-2’s closest relatives, I found it One in five bat handlers in Laos had antibodies against coronaviruses.

The majority of these indirect infections go away on their own, researchers say. In a study published in the journal Science in AprilIn computer simulations, Worby and colleagues show that for SARS-CoV-2 to spread to cause major epidemics, the urban environment is critical—without it, it would die very quickly.

“It is more likely hundreds, if not thousands of times,” that a wildlife trader who was exposed to an ancestor of SARS-CoV-2 — either from bats or other animal species — brought the infection to Huanan more than a researcher who went to collect bat samples, returned to Wuhan with the pathogen and then brought him to Huanan, says Wang.

Worobey agrees. Based on numerous evidence, he is now convinced not only that the link of the epidemic to the Huanan market is real, but also that one of the ancestors of SARS-CoV-2 jumped from animal to human. “This is a much greater possibility than any other scenarios based on what we know now,” he says.

He adds that preliminary findings from ongoing work by his group and others will help advance the case further: “They all point in the same direction.”

The writing of this article was supported by a grant from the Pulitzer Center.



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