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The trajectory of the new SARS-CoV-2 coronavirus until 2019. appeared in central China in December, it remains an enigma, but scientists say it is possible to unravel.
In Wuhan, where the first group of cases appeared, researchers involved in the search for Covid-19 have identified four hypotheses that could explain the genesis of the virus, including two that caused controversy, although considered unlikely.
Beijing adheres to the theory that the virus was spread through contaminated food or packaging, and the Trump administration argued that this may have been the result of an accident in the laboratory.
However, the most plausible theory, according to experts involved in the mission, has to do with China’s wildlife trade. Wildlife hunted for the food, fur and traditional medicine business in 2016 amounted to about 520 billion. yuan ($ 80 billion).
Juan’s food market in central Wuhan, the city where the first major Covid-19 outbreak was detected, was selling live animals that could have spread the coronavirus infection.
It cannot be ruled out that they acted as transmitters of the virus, transmitting it from bats (the most likely primary source) to humans, says Peter Daszak, a zoologist who was involved in a joint study earlier this year when international experts visited Wuhan. after the Chinese government’s wall of silence.
Peteris daszakas
“The main conclusion of this phase of the investigation, of course, the investigation is not over yet, is that exactly the same path that SARS has taken has led to the emergence of the Covid infection,” said Daszak, who is also a New York-based non-profit company President of the EcoHealth Alliance, whose goal is to prevent virus outbreaks around the world.
The investigators’ report, scheduled to be delivered this week (delayed by political disagreements), is unlikely to be far from final. More research is planned, including outside of China, to encrypt the Covid-19 story, which is vital in trying to understand how to recover from the disease and help prevent similar catastrophes in the future.
Although hunting the virus has become the political football of the world’s superpowers, Daszak says he believes science will ultimately prevail. Important facts about where SARS-CoV-2 originated and how it spread will be revealed in the coming years, he said on March 10. Chatham House webinar.
SARS prevalence
Farmed and wild civets, a small nocturnal mammal for human consumption in China, were charged in 2003. The spread of the SARS virus in markets in southern Guangdong province. The researchers later discovered that the infection originated in bats, a natural reservoir for coronavirus.
It is highly likely that both species were found in markets where live animals were kept in overcrowded cages, which allowed the bat-borne virus to adapt and intensify before being transmitted to humans, primarily to market workers and breeders of the bats. animals.
Researchers say a similar scenario could have occurred with Covid-19. A study of the first 99 patients treated at an infectious disease hospital in Wuhan found that half of them had dealings with the Huanan seafood market, which allegedly also sold live animals, some illegally caught from the wild and slaughtered in front of them. customers.
The virus may have been transmitted to humans via an infected animal that was sold at Juan Market or elsewhere in Wuhan, says Sydney microbiologist Dominic Dwyer, who was part of a WHO team that visited. the Chinese city in February.
However, questions remain about the role of the market in the spread of the infection.
After investigating after the market in 2019 closed in December, no infected animals could be found. However, many contaminated surfaces have been found that could have helped spread the virus to infected people or contaminated animal products.
The confusion is compounded by the fact that the first known Covid-19 patient experienced symptoms four days before the first market-related events.
Analysis of the SARS-CoV-2 samples collected in mid-December revealed subtle genetic differences between them. This means that the virus could secretly circulate in the community for weeks before doctors were warned by several seriously ill patients with a mysterious viral pneumonia.
The initial transmission of the coronavirus to humans was likely followed by rapid adaptation of the virus, says Joel O. Wertheim, an associate professor of medicine at the University of California, San Diego. The virus may have been transmitted more than once and disappeared because infected people continued to not transmit the virus to anyone, Mr. Wertheim and colleagues commented on March 18. in an article published in the journal Science.
Eventually, the virus infected one person who passed it on to a few more people, who in turn passed it on to others. Maybe that person was a super distributor.
All of this could have happened in Juan’s market, Wertheim said in an interview. “The market could have been the place where the virus was transmitted to humans,” he said.
Current evidence suggests that the bazaar was where SARS-CoV-2 was distributed, but not necessarily where it originated, Dwyer says.
“Perfect place”
“After visiting that market, you realize that it is the perfect place for an outbreak, because there are many people, many stalls, many animal products and the ventilation and drainage system is far from developed,” he said. he said in an interview. “It’s no wonder an outbreak has occurred there.”
A team of WHO scientists has found evidence that wildlife farms in southern China were supplying produce to Juan Market vendors, Daszak told US National Radio. The investigation identified a route from provinces of the United States. South like Yunnan (where the closest SARS-CoV-2 coronavirus was found in bats in 2013) to Wuhan, he said in a Chatham House webinar.
“It shows the connection and how the virus could really pass from nature to people or animals raised in the region and then somehow be brought to market,” Daszak said. – This is a really important discovery. This initial knowledge of the route of the virus movement should be expanded as soon as possible. “
The Chinese government has been promoting wildlife farming for decades as it has helped increase the income of the rural population. These practices provided a particularly valuable alternative source of meat following the African swine fever outbreak in 2018.
The deadly outbreak caused an unprecedented pork shortage, researchers from the South China Agricultural University and the University of Glasgow said in a study published in February without official review. China usually consumes half of the world’s pork.
Squirrels, thorns
Although the shortage of pork has led to the consumption of wild animals, eating birds, snakes, rats, squirrels, porcupines and other non-domestic animals has been popular in China in the past, especially in the southern provinces of the country, the researchers . saying.
They cited 2004. A survey by the China Wildlife Conservation Association found that 46 percent of the townspeople tried bushmeat at least once, and 2.7 percent. they ate them constantly. A 2017 survey in January found 52 percent. 40% of the surveyed markets traded in wild animals and 40%. restaurants offered dishes of wild animals.
Much of this trade is believed to have ended just over a year ago. After President Xi Jinping warned that eating wildlife posed a serious threat to public health, the Standing Committee of the National People’s Congress in 2020. February 24 decided to expand the scope of China’s Wildlife Protection Law to ban the consumption of almost all wildlife.
With foreign countries criticizing the government’s handling of the pandemic in its early days, official Chinese rhetoric now aims to incite doubts about whether the pathogen actually occurred on the country’s territory.
However, not surprisingly, China decided to stop the wildlife trade a year ago, Daszak notes.
“It is obvious that in 2020. in February, the Chinese themselves thought it was the most likely path,” the coronavirus reached Wuhan, the scientist said.
“And when we get the WHO report … we’ll see that it was probably the most likely path,” he says.
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