Outside the closed Huanan Seafood Market in Wuhan in January.
Photographer: Hector Retamal / AFP / Getty Images
Scientists retracing the The origins of the Covid-19 pandemic believe they have identified a possible source of transmission: the flourishing wildlife trade in China.
The eagerly awaited findings of experts convened by the World Health Organization and the Chinese government are expected to show parallels with the 2002 spawning of Severe Acute Respiratory Syndrome, or SARS, a bat-borne coronavirus spread by civets that killed 800 people. How far SARS-CoV-2 – as the new coronavirus is known – traveled before it emerged in central China in December 2019 remains a mystery, although what researchers say can be resolved.
In Wuhan, where the first cluster of cases occurred, scientists involved in the hunt identified four hypotheses to explain the genesis of the virus, including two that fueled controversy even though they were deemed unlikely. The idea that the virus was introduced via contaminated food or packaging is an idea adopted in Beijing, while the Trump administration has said it may have been the result of a laboratory accident. But the most plausible theory, say experts involved in the mission, concerns China’s wildlife trade for food, furs and traditional products. medicine, a business worth around 520 billion yuan ($ 80 billion) in 2016.
Read more: Where are we in the search for the origin of the coronavirus?
Live animals susceptible to coronavirus infection were present at the Huanan food market in downtown Wuhan, the city where the first major outbreak of Covid-19 was detected. It is possible that they acted as conduits for the virus, carrying it from bats – probably the main source – to humans, says Peter Daszak, a zoologist who was part of the joint research effort, who saw international experts visit Wuhan earlier this year after months of blockade by the Chinese government.
“The main conclusion of this stage of the work – and it is not over yet of course – is that the same route through which SARS emerged was very much alive for the emergence of Covid,” said Daszak, who is also president of EcoHealth Alliance, a New York-based nonprofit that works to prevent viral epidemics around the world.
The scientists’ report, scheduled for publication this week after delays due to political disputes are probably far from conclusive. Further studies are planned, including outside of China, with deciphering the history of the creation of Covid-19 essential to understanding how best to thwart its resurgence and help prevent similar disasters in the future.
China makes it harder to solve mystery of Covid origin
As the hunt for the origin of the virus has turned into political football for the world’s superpowers, Daszak says he believes the scientific process will prevail. Important data on the origin of SARS-CoV-2 and its emergence will be uncovered over the next few years, he told a conference on March 10. webinar hosted by Chatham House.
Spread of SARS
High and wild civets, a small nocturnal mammal eaten in China, have been accused of spreading the SARS virus in a market in the southern province of Guangdong in 2003. Scientists later discovered that the infection was from horseshoe bats, a natural reservoir of coronavirus.
The two species probably collided in markets where live animals are caged crowded conditions, potentially allowing bat-transmitted virus to adapt and amplify before it spills over to humans, initially among workers and those who handle animals.
Scientists working on the origins hunt say a similar scenario may have played out with Covid-19. Study of the first 99 patients treated at an infectious disease hospital in Wuhan has been found half was linked to the Huanan seafood market, which would have sold live animals, some illegally captured in the wild and slaughtered in front of customers.
It is possible that the virus was introduced by an infected animal that was sold at Huanan Market or elsewhere in Wuhan, said Dominic Dwyer, a Sydney microbiologist who was part of the team convened by the WHO to traveled to the Chinese city in February.
Yet questions remain about the ultimate role of the market.
Testing after it closed in December 2019 failed to detect infected animals. Contaminated surfaces were widespread, compatible with the introduction of the virus by infected persons or contaminated animal products. To compound the confusion, the first known Covid-19 patient developed symptoms four days before the first cases were released to the market.
Revisiting the other markets of Huanan and Wuhan (Video)
Analysis of SARS-CoV-2 samples collected in mid-December revealed subtle genetic differences between them. The variation indicates that the virus may have circulated surreptitiously for weeks in the community before doctors were alerted via a handful of critically ill patients with a mysterious viral pneumonia.
The initial outflow of the coronavirus into a human was likely followed by rapid adaptation of the virus, said Joel O. Wertheim, associate professor of medicine at the University of California, San Diego. It is possible that the virus has been transmitted several times and died out when those infected did not pass the virus on to anyone, Wertheim and colleagues said in a March 18 article in the journal Science. Eventually, the virus infected someone who passed it on to several people, who also passed it on to others, possibly during a super-spread event.
Perhaps this is the Huanan market where it happened, Wertheim said in an interview. “The market may have played a key role in the installation of the virus in humans.”
Current evidence suggests the market is where SARS-CoV-2 was amplified, and not necessarily where it was born, Dwyer said.
‘The perfect place’
“When you visit the market, you realize that this is the perfect place for an epidemic to occur because it is crowded, lots of stalls, lots of animal products, and ventilation and drainage are a little suboptimal, ”he said in an interview. “It’s no surprise that we had an explosion there.”
The WHO research team found evidence that southern Chinese wildlife farms were supplying vendors to the Huanan market, Daszak told US National Public Radio. He also found a route from southern provinces like Yunnan – where the The closest known coronavirus to SARS-CoV-2 was found in horseshoe bats in 2013 – in Wuhan, he told the Chatham House webinar.
“It provides a link and a route through which a virus could convincingly spread from wildlife to people or animals raised in the area and then shipped to a market by some means,” Daszak said. “It’s a really important clue. These beginnings of understanding a path must be followed fairly quickly. ”
For for decades, the Chinese government has encouraged the breeding of wild animals to boost rural incomes. The practice provided an alternative source of particularly valuable meat after African swine fever first emerged in 2018. The deadly outbreak has led to an unprecedented shortage of pigs, researchers from South China University of Agriculture and University of Glasgow said. in a study published in February without formal peer review. China typically consumes half of the world’s pork.Squirrels, porcupines
While the shortage of pigs has spurred the consumption of wild animals, eating birds, snakes, bamboo rats, squirrels, porcupines and other non-domesticated animals were already popular, especially in the southern provinces, the researchers said.
They cited a 2004 survey by the China Wildlife Conservation Association which found that 46% of urban residents had consumed wildlife and 2.7% were regular consumers. A January 2017 survey found that 52% of the markets they surveyed were the wildlife trade, while 40% of the restaurants offered wildlife dishes.
Much of the the trade would have ended a little over a year ago. After President Xi Jinping warned that eating wild animals posed immense risk to public health, the Standing Committee of the National People’s Congress decided on February 24, 2020 to extend the scope of China’s wildlife protection law to ban the consumption of almost all wild animals.
Amid international criticism of its handling of the early days of the pandemic, official rhetoric from China aims to cast doubt on the pathogen originated from its borders. But China targeted the wildlife trade a year ago for a reason, Daszak told NPR.
“The reason was that in February 2020, they thought it was the most likely route” for the coronavirus to reach Wuhan, he said. “And when the WHO report comes out … we think that’s the most likely route as well.”
