A lab leak in Wuhan versus a natural hop from bats: The evidence for each theory of the coronavirus’ origin

Guards stand outside the Wuhan Institute of Virology on February 3, 2021.
Hector Retamal/AFP via Getty

The idea that the coronavirus leaked from a Wuhan lab has not been disproved, though a WHO report said it’s extremely unlikely.
The virus probably jumped to people from animals.
Here’s a breakdown of the evidence in favor of a lab leak and a natural spillover from animals.
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It’s the theory that refuses to die: Might the coronavirus have leaked out of a Wuhan lab?
As long as the mystery of the virus’ origin remains unsolved, the question will persist. Increasingly, global public-health leaders are calling for more thorough investigations into the possibility.
That group includes Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, andTedros Adhanom Ghebreyesus, director-general of the World Health Organization. Although a month-long WHO investigation in Wuhan concluded that the coronavirus most likely spilled over to people from animals – possibly at wildlife farms – the group found no definitive proof of that. Nor could they rule out a lab leak.
So Tedros said in March that he does "not believe that this assessment was extensive enough."
Fauci, meanwhile, said during a Senate hearing this month that the "possibility certainly exists" that the pandemic started because of a lab accident.
The former head of the Food and Drug Administration, Scott Gottlieb, has also said there is some circumstantial evidence favoring a lab leak, as has Robert Redfield, former director of the Centers for Disease Control and Prevention.
Here’s what to know about each theory – a lab leak and natural spillover from animals – and the key pieces of evidence supporting each.
The lab-leak hypothesisEighteen scientists from the US, UK, Canada, and Switzerland recently published a letter saying they think the lab-leak theory remains viable.
Questions about a such a leak generally center on the Wuhan Institute of Virology (WIV), a high-level biosafety lab where some scientists had been studying coronaviruses prior to the pandemic. Wuhan, of course, is the city where authorities reported the first cluster of COVID-19 cases. Below are the main reasons people think the virus might have emerged from the lab.

An aerial view of the campus of the Wuhan Institute of Virology on May 27, 2020.
Hector Retamal/AFP via Getty

The Wuhan Institute of Virology was researching coronaviruses before the pandemicScientists at the WIV research infectious diseases – collecting, storing, and genetically analyzing samples of the most dangerous and infectious pathogens known to humankind. The institute boasts a biosafety level 4 lab, one of only a few dozen in the world.
Peter Ben Embarek, a WHO scientist specializing in animal disease, was part of the team that investigated the institute in January. He said it’s natural to speculate about a link – especially given that the WIV moved to a new location in early December 2019, which happens to be just miles from the Huanan Seafood Market.
The first cluster of coronavirus cases in Wuhan was linked to the market, but it turned out to simply have hosted an early superspreader event.
"Even the staff in these labs told us that was their first reaction when they heard about this new emerging disease, this coronavirus: ‘This is something coming out of our labs,’" Ben Embarek said in March.
But after investigating that possibility, the WIV staff said they found no evidence that samples of the new coronavirus had been stored at the institute prior to December 2019. Records reviewed by the WHO did not indicate that any viruses closely related to the new coronavirus were kept in any Chinese lab before that month. The records also did not show any viruses that, when combined, could have produced the new coronavirus.
But Embarek’s team also said they weren’t given full access to the Wuhan institute’s data.
WHO investigators couldn’t conduct a full audit of the labs

Peter Daszak, Thea Fischer, and other members of the WHO team investigating the coronavirus’ origins arrive at the Wuhan Institute of Virology on February 3, 2021.
Hector Retamal/AFP via Getty

Embarek said he and his co-investigators didn’t do a full audit of the WIV. The WHO team spent just hours at the institute – which isn’t enough time to pour over files, databases, or freezer inventories. The institute’s staff also did not share all of its records or safety logs.
That’s why Tedros has said he does "not believe that this assessment was extensive enough."
He, Fauci, and many others are still calling for a full investigation of the lab.
However, Joanna Mazet, an epidemiologist at the University of California, Davis, has worked directly with WIV researchers, including one of its prominent virologists, Shi Zhengli. Mazet told Insider that the lab’s records are above reproach.
"She is absolutely positive that she had never identified this virus prior to the outbreak happening," Mazet told Insider, referring to Shi’s work.
WIV staff members got sick with ‘COVID-like’ symptoms in November 2019A report uncovered by the Wall Street Journal revealed that three WIV staff got sick and were hospitalized more than a month before experts identified the first COVID-19 cases in Wuhan. The report – which an intelligence official said lacked sufficient corroboration – said the workers’ symptoms were "consistent with both COVID-19 and common seasonal illness."
According to virologist Marion Koopmans, the WHO team was aware that some WIV staff had gotten sick in the fall of 2019. They’d chalked the incidents up to season illness because blood samples taken from WIV staff in the months ahead of the pandemic all tested negative for coronavirus antibodies. (Such samples are taken routinely from biosafety lab workers to monitor their health.)
The coronavirus is easily transmissible among humansGenerally, it takes time for a new virus to adapt to be able to spread easily from person to person.
So people like Redfield point to the coronavirus’ highly infectious nature as evidence that it may be a product of "gain-of-function" research. In this kind of work, scientists tweak viruses with the goal of making the pathogens more transmissible or deadlier in order to figure out how to stop future pandemics.
"I do not believe that this somehow came from a bat to a human, and at that moment in time that the virus came to the human, became one of the most infectious viruses that we know in humanity for human-to-human transmission," Redfield told CNN in March.
But Fauci said that same month that it’s more likely that the coronavirus got good at jumping between people while spreading "below the radar" in China in late 2019. Growing evidence suggests COVID-19 was spreading for several weeks, if not months, before the first cases were reported.
That allowed the virus "to be pretty well adapted when first recognized," Fauci said.
Lab leaks happen, and US intelligence suggested the WIV had poor safety protocol

A worker in directs members of the WHO team on their arrival at the airport in Wuhan in China’s Hubei province, January 14, 2021.
AP Photo/Ng Han Guan

Three years ago, US officials visiting Wuhan sent a pair of memos to the State Department warning of inadequate safety measures at the lab. The institute seems to have made rigorous changes since then, though, and the WHO team was satisfied with the lab’s protocols.
Ben Embarek said the WIV housed a "state-of-the-art lab," which is part of the reason his team thinks it’s "very unlikely that anything could escape from such a place."
Mazet, too, has said it’s "highly unlikely this was a lab accident," since she worked with WIV staff to develop and implement a "very stringent safety protocol."
Still, Ben Embarek noted in February that "accidents do happen."
"We have many examples in many countries in the world of past accidents," he said.
Although such accidents are rare, there have been four instances in which SARS has leaked from laboratories in Taiwan, Singapore, and Beijing.
The wildlife farms where the virus might have emerged are 1,000 miles from Wuhan

A cyclist rides in front of the closed Huanan seafood market in Wuhan on February 9, 2021.

The wildlife farms where the WHO team thinks the coronavirus most likely emerged are 800 to 1,000 miles from Wuhan.
But Koopmans said the WHO team found that rabbits and ferret-badgers sold at Huanan Seafood Market were transported there from regions in China where bats harbor viruses similar to the new coronavirus. Both rabbits and ferret-badgers are susceptible to coronavirus infection, so could have passed it to farmers who traveled into the city, or to market shoppers.
Still, just because the first reported cluster of cases emerged in Wuhan doesn’t mean that’s where the pandemic truly began. Wuhan is the largest city in Hubei province, and people from all over central China travel though the region. Once the virus arrived in a dense, urban environment, it makes sense it would spread rapidly there.
The animal-spillover theoryAfter the WHO’s investigation in Wuhan, the team determined the coronavirus "most likely" jumped from bats to people via an intermediary animal host at a wildlife farm. This kind of spillover has been the leading theory throughout the pandemic primarily because 75% of new infectious diseases come to us from animals. Plus, the coronavirus’ genetic code is very similar to that of other coronaviruses found circulating in bats. Here’s the evidence supporting this idea.

Members of the World Health Organization’s team investigating the origins of the coronavirus pandemic attend a press conference in Wuhan on February 9, 2021.
Kyodo News/Getty

The WHO concluded that an animal-to-human hop is ‘most likely’In southern China, the WHO found, people interacted closely with animals like civets, minks, pangolins, rabbits, and raccoon dogs at farms where these animals were bred in captivity for food.
All of these species can be infected by the new coronavirus, and any contact with an infected animal or its poop can allow a virus to jump from animals to people. That’s why the WHO found this to be the "most likely" origin of the pandemic. Still, the team examined 80,000 animals from 31 provinces across China and didn’t find a single case of the coronavirus. China shut down the specific wildlife farms in question in February 2020, and the WHO researchers weren’t given access to samples from animals from these farms.
Plus, according to Tedros, the WHO experts had difficulties accessing COVID-19 infection data and patient blood samples from in and around Wuhan – which could also cast doubt on the team’s conclusions.
The scientists behind the recent letter about the lab-leak theory wrote that in the WHO’s report, that possibility was "not given balanced consideration." Only four of the report’s 313 pages discuss evidence of a lab accident.
SARS-CoV-2 shares 97% of its genetic code with other coronaviruses found in bats

A greater horseshoe bat, a relative of species that was the original host of the SARS virus.
De Agostini/Getty

Bats are common virus reservoirs. Cross-species hops from bat populations also led to the outbreaks of Ebola, SARS, and the Nipah virus.
A wealth of evidence shows similarities between the new coronavirus and coronaviruses in bat populations. A May 2020 study, for example, revealed that the new coronavirus shared 97.1% of its genetic code with a coronavirus called RmYN02, which was found in bats in China’s Yunnan province between May and October 2019. A paper in the journal Nature, published by Shi’s group at the WIV, found that a coronavirus named RaTG13 was a 96.2% match.
RaTG13, it turns out, is the same virus that Shi and her WIV colleagues collected samples of nearly a decade ago in a remote mine. Six miners got a mysterious pneumonia-like illness there in 2012, and three of them died, according to the Wall Street Journal. Blood samples from the miners didn’t test positive for the new coronavirus, however.
When Shi and co-authors published their genetic analysis of RaTG13 last year, they did not disclose its link to the miners’ deaths.
Three-quarters of infectious diseases come from natural spillover

A farmer checks rabbits at his farm on January 29, 2021 in Chongqing, China.
Qu Mingbin/VCG via Getty

Three out of every four emerging infectious diseases come to us from other species; these pathogens are known as zoonotic diseases.
Peter Daszak, a disease ecologist with EcoHealth Alliance and a member of the WHO investigation team, told NPR in April 2020 that "1 to 7 million people" are exposed to zoonotic viruses in Southeast Asia each year.
"That’s the pathway. It’s just so obvious to all of us working in the field," he said.
Daszak and the EcoHealth Alliance have worked with and funded WIV research in the past, though that funding was canceled last year. Some people suggest Daszek has a bias against the lab-leak theory, since it could lead his organization to be seen as culpable for funding research that led to the pandemic.
Still, spillover events have doubled – if not tripled – in the last 40 years, according to Dennis Carroll, the former director of USAID’s emerging threats division. That’s because people are increasingly turning wild areas into farms and fields for livestock production.
"Whatever future threats we’re going to face already exist; they are currently circulating in wildlife," Carroll told Nautilus Magazine last year.
Read the original article on Business Insider

Source: https://www.businessinsider.com/wuhan-lab-leak-animal-spillover-coronavirus-origin-questions-2021-5

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