An inner story of how one scientist concluded that a covid started spilling over into a market in Wuhan

An inner story of how one scientist concluded that a covid started spilling over into a market in Wuhan

“Penalties for violators can be harsh,” says Zhou Zhaomin, an expert on Chinese 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 large enough numbers could result in life imprisonment.

But law enforcement has been poor. Several researchers told the MIT Technology Review that it was a “public secret” that illegal wildlife trafficking was widespread in China.

Indeed, Zhou and his colleagues conducted research between 2017 and 2019 which found that four markets in Wuhan, including Huanan, sold a total of nearly 48,000 wildlife of 38 species, almost all of which were sold alive, in cages and stacked in cramped, unhygienic conditions perfect for virus transmission. Animals – wild-caught or untamed species bred – include species susceptible to SARS-CoV-1 and SARS-CoV-2, such as civets, martens, badgers and raccoons.

That study, published in June of the year Scientific Reports, found that all the wildlife trade the researchers investigated was illegal. Many vendors sold protected species; none published the required certificates indicating the source of the animals or that they were disease-free.

This means that as soon as Juanan was involved in the early cases of covida-19, vendors selling live mammals, most likely illegally, would flee to avoid jail time, while law enforcement agencies are unlikely to acknowledge that such activities existed at all. Given that, it was not surprising that the Chinese authorities did not find any clues regarding the sale of live animals on the Huanan market, says Hanage from Harvard.

Restrictions on wildlife trade were minimal after SARS, which allowed scientists almost unrestricted access to animals and traders in wet markets in Guangdong – but even that was not enough to help them determine the source of SARS. While they quickly came across viruses in the civets, badgers and raccoon dogs that were more than 99% identical to SARS-CoV-1, subsequent research has not shown widespread virus circulation, either in the wild or in agricultural conditions. That is the dominant attitude civets got the virus during trading, most likely from bats that were bought and sold at the same time.

Now, 18 years later, the situation is strikingly similar. It seems to exist there is no widespread SARS-CoV-2 circulation in animals. None of the approximately 80,000 samples tested by the Chinese team of the World Health Organization mission in search of the origin of the pandemic – including the main suspects such as pangolins, civets, badgers and bamboo rats – contained the virus.

However, many scientists are still largely in favor of the theory that wet markets played a key role in launching Covid-19. Although all eyes are on Yunnan and other parts of Southeast Asia as the most likely sites of the pandemic, Hanage says it’s “not crazy” to suggest that Hubei Province in Wuhan could have been where SARS-CoV-2 naturally occurred.

Indeed, scientists from the Wuhan Institute of Virology have discovered Coronaviruses similar to SARS in bats in Hubei. Although they did not systematically test farmed animals for coronavirus infection throughout the province, in little known study conducted after SARS, they found that seven civets they tested on a farm in the province in 2004 were infected with relatives of SARS-CoV-1. Several research teams in China and the U.S. are trying to find out where the animals got the virus from, whether coronavirus infection is more common among civets than previously thought, and what impact this could have on our understanding of the origin of covid-19.

Constant overflow

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

One such critic is Alina Chan, a molecular biologist at the Broad Institute of MIT and Harvard (this publication is owned by MIT, but is editorially independent of it). The central question, she said a recent webinar organized by the journal Science, the virus arrived in 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 that goes down to these places [knew] they would find SARS viruses, bringing them all the way to the city of Wuhan, thousands of miles away, ”she said. However, there is no evidence of such wildlife trade routes, she added.

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 of Singapore. The cave that gave the closest relative of the SARS-CoV-1 bat is almost 1,000 miles away from Guangdong Market where the first cases of SARS occurred – similar to the distance between Wuhan and the place where one of the closest relatives of the SARS-CoV-2 bats is discovered.

And it is becoming increasingly clear that people in close contact with wild animals are infected with the coronavirus much more often than previously thought.

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

Michael Worobey

Studies show that up to 4% of people living near bats i they work closely with wild animals in southern China, they are infected with deadly animal-borne viruses, including coronaviruses. Lao and French team, which discovered of the closest relatives of SARS-CoV-2, discovered it every fifth bat carrier in Laos had antibodies against these coronaviruses.

Most of these transient infections die out on their own, the researchers say. In a study published in the journal Science in April, Worobey and colleagues show in a computer simulation that the urban environment is critical for the spread of SARS-CoV-2 to cause major epidemics – without it it would become extinct very quickly.

“Hundreds, if not thousands, times more likely” that a wildlife trader who was exposed to SARS-CoV-2 progenitor – whether from bats or other animal species – brought the infection to Juanan than that a researcher who went to collect bat samples were returned to Wuhan with the pathogen and then brought to Huanan, Wang says.

Worobey agrees. Based on much evidence, he is now convinced not only that the pandemic’s link to the Huanan market is real, but also that this is where the predecessor of SARS-CoV-2 jumped from animal to human. “It’s much more likely than any other scenario based on what we know now,” he says.

Preliminary results from the ongoing work of his group and others will help further strengthen the case, he added: “Everyone is pointing in the same direction.”

The reporting for this article was supported by a donation from the Pulitzer Center.

Source link

Leave a Reply