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Scientists tracking the The origins of the Covid-19 pandemic are believed to have identified a possible source of transmission: China’s thriving wildlife trade.
The expected findings of experts called by the World Health Organization and the Chinese government are expected to show parallels with the spread in 2002 of severe acute respiratory syndrome, or SARS, a bat-borne coronavirus spread by civets that killed 800 people. The path taken by SARS-CoV-2 – as the new coronavirus is known – before emerging in central China in December 2019 remains a mystery, although researchers say it can be resolved.
In Wuhan, where the first group of cases occurred, the scientists involved in the hunt identified four hypotheses to explain the genesis of the virus, including two that generated controversy, although they were considered unlikely. The idea that the virus was introduced through contaminated food or packaging is adopted in Beijing, while the Trump administration 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 traditional food, fur and products medicine, a business worth about 520 billion yuan ($ 80 billion) in 2016.
Read More: Where are we in the hunt for the origin of Coronavirus?
Live animals susceptible to coronavirus infection were present at the Huanan food market in central Wuhan, the city where the first major outbreak of Covid-19 was detected. It is possible that they acted as drivers of the virus, transporting it from bats – probably the primary 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 phase of the work – and it is not yet over, of course – is that the same path by which SARS emerged was alive and well for the emergence of Covid,” said Daszak, who is also president of EcoHealth Alliance, a New York-based non-profit organization that works to prevent viral outbreaks worldwide.
The scientists’ report, due for release 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 Covid-19’s creation vital to understanding how best to prevent its resurgence, and to help prevent similar disasters in the future.
China is making it harder to solve the mystery of where Covid started
Although the hunt for the source of the virus has become a political football game for the world’s superpowers, Daszak says he believes the scientific process will prevail. Significant data on the origin of SARS-CoV-2 and how it emerged will be discovered in the years to come, he said during a webinar organized by Chatham House.
SARS Spread
Cultivated and wild civets, a small nocturnal mammal consumed in China, were held responsible for spreading the SARS virus in a market in southern Guangdong province in 2003. Scientists later discovered that the infection originated horseshoe bats, one natural reservoir of coronavirus.
A civet at a market in Guangdong in 2002.
Photographer: Richard A. Brooks / AFP / Getty Images
The two species probably collided in markets where live animals are caged in overcrowded conditions, potentially allowing the virus transmitted by bats adapt and amplify before spreading to humans, initially between workers and those who handle animals.
Scientists working on hunting for origin say a similar scenario may have occurred with Covid-19. A study of the first 99 patients treated at an infectious disease hospital in Wuhan found half was linked to the Huanan seafood market, which also supposedly sold live animals, some caught illegally in the jungle and slaughtered in front of customers.
It is possible that the virus was introduced through an infected animal that was sold in the Huanan market or elsewhere in Wuhan, said Dominic Dwyer, a microbiologist in Sydney who was part of the team convened by WHO who traveled to the Chinese city in February.
Still, doubts remain about the final role of the market.
Tests after closing in December 2019 failed to detect any infected animals. Contaminated surfaces were widespread, compatible with the virus being introduced by infected people or contaminated animal products. To compound the confusion, Covid-19’s first known patient developed symptoms four days before the first cases linked to the market.
Revisiting Huanan and other Wuhan markets (Video)
An analysis of SARS-CoV-2 samples collected in mid-December found subtle genetic differences between them. The variation indicates that the virus may have been secretly circulating for weeks in the community before doctors were alerted to it by a handful of critically ill patients with a mysterious viral pneumonia.
The original leak of the coronavirus to a human was probably followed by a rapid adaptation of the virus, said Joel O. Wertheim, an associate professor of medicine at the University of California, San Diego. It is possible that the virus has been transmitted several times and it went extinct when the infected individuals did not transmit the virus to anyone, Wertheim and his colleagues said in an article published on March 18 in the journal Science. Eventually, the virus infected someone who passed it on to several people, who also passed it on to others, possibly in an over-spreading event.
The Huanan market may have been where this occurred, Wertheim said in an interview. “The market may have been the key for the virus to install itself in humans.”
Current evidence suggests that the market is where SARS-CoV-2 was amplified, and not necessarily its birthplace, said Dwyer.
‘Perfect place’
“When you visit the market, you realize that it is a perfect place for an outbreak to occur because it is crowded, many stalls, many animal products and ventilation and drainage are slightly below ideal,” he said in an interview. “It is no surprise that there was an explosion there.”
The WHO research team found evidence that Wildlife farms in southern China provided vendors in the Huanan market, Daszak told US National Public Radio. He also found a route to southern provinces such as Yunnan – where the The closest known coronavirus to SARS-CoV-2 was found in horseshoe bats in 2013 – in Wuhan, he said on the Chatham House webinar.
WHO team members arrive at the Chinese Center for Disease Control and Prevention in Wuhan in February.
Photographer: Hector Retamal / AFP / Getty Images
“It provides a link and a path by which a virus can convincingly spread wildlife to people or animals raised in the region and then be sent to the market by some means,” said Daszak. “This is a very important clue. The beginning of understanding a path needs to be followed very quickly. “
For decades, the government of China has promoted the breeding of wild animals to increase rural income. The practice provided an especially valuable alternative source of meat after African swine fever emerged in 2018. The deadly outbreak resulted in an unprecedented shortage of pork, said researchers at South China Agricultural University and the University of Glasgow in a study that was launched in February without formal peer review. China normally consumes half the world’s pork.
Squirrels, Porcupines
While the shortage of pork has reinforced the consumption of wildlife, eating birds, snakes, bamboo rats, squirrels, hedgehogs and other undomesticated 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 surveyed were wildlife trade, while 40% of the restaurants provided wild animal dishes.
Much of the trade supposedly ended just over a year ago. After President Xi Jinping warned that wildlife consumption represented a major immense risk to public health, the Standing Committee of the National People’s Congress decided on February 24, 2020 to expand the scope of China’s Wildlife Protection Act to ban the consumption of almost all wild animals.
Amid international criticism of the treatment of the early days of the pandemic, China’s official rhetoric focuses on creating doubts that the pathogen originated within 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 believed this was the most likely route” for the coronavirus to reach Wuhan, he said. “And when the WHO report is published … we believe it is the most likely path as well.”