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What is the date of the appearance of COVID-19?
There is no certainty. All we know is that the first cases were detected in the Chinese city of Wuhan a year ago, before the disease spread to Asia and then to the world.
“We believe the first cases in Wuhan date back to early December,” the World Health Organization (WHO) says on its website.
“But the place where an epidemic is detected for the first time is not necessarily where it started”, adds the WHO, according to which “it cannot be excluded that the virus circulates elsewhere, silently”.
In recent months, researchers from several countries have ensured that the cases go unnoticed long before December 2019, based on analyzes of wastewater and blood samples.
But these claims “have not been confirmed” for lack of “clear evidence” of their strength, points out Etienne Simon-Lorière, head of the RNA virus evolutionary genomics unit at the Pasteur Institute (Paris).
To establish the family tree of the virus, researchers rely primarily on genetics.
These analyzes “allow us to better understand the dynamics of transmission, in particular how the virus may have evolved over time and how different infection centers can be linked together,” according to the WHO.
The organization has assembled an international team of 10 scientists whose mission is to trace the origins of the virus.
They will have to investigate the suspicious animals and how the first patients may have been infected.
How was the virus born?
Scientists agree that the disease is of animal origin. “The big question mark is what led to the transition to man,” Etienne Simon-Lorière explains to AFP.
It is very likely that the animal causing the virus is the bat, “a great reservoir of coronavirus,” he adds.
The intermediate animal has not yet been discovered, as it is unlikely that the SARS-CoV-2 virus passed directly from bats to humans.
The pangolin was suspected very early, based on genetic analysis. But there are no certainties.
The WHO mission will have to clarify this point by investigating other animals sold at Wuhan’s Huanan market, to which most of the early cases were related. And your research may be guided by clues you didn’t have at the start of the pandemic.
“It may be that the intermediary is an animal that has a receptor for the virus very close to what we see in humans,” notes Etienne Simon-Lorière.
This receptor is a protein called ACE2, which the virus binds to to enter cells. The family of mustelids (minks, ferrets, etc.), for example, possesses a receptor very close to that of humans, which does not happen with other animals.
Nothing guarantees, however, that the answer will be found.
“How an infectious disease crosses the animal-human barrier is an enigma that can take years to solve,” recalls the WHO, according to which “the introduction of a new virus into the human population is one of the greatest mysteries. that an epidemiologist can hope to uncover “.
“It’s a very random treasure hunt. For Ebola, we have never been able to find it,” adds Etienne Simon-Lorière.
And the laboratory?
In the spring, in the face of diplomatic tensions, US President Donald Trump said the virus accidentally escaped from a specialized laboratory in Wuhan. China has denied the allegations, but the debate is recurring.
“As long as the intermediate host is not found, the hypothesis of accidental escape cannot be ruled out by the scientific community,” virologist Etienne Decroly recently said on the website of the French research center CNRS.
“It is a scenario that we are obliged to list, even if in practice it seems implausible, because this would involve a lot of secrecy and a lot of lies,” estimates Etienne Simon-Lorière.
The scientific community, however, rejects another hypothesis often cited by conspiracy circles, according to which the coronavirus was fabricated in the laboratory.
“All the elements of its genome have already been observed in nature, mainly in bat coronaviruses. There is therefore no indication that it could have been man-made,” explains Etienne Simon-Lorière.
What are the deadlines for the WHO mission?
After sending a reconnaissance team in July, WHO expects to be able to “deploy” to China “soon,” he said on November 23.
Science is not everything, however, and diplomatic considerations come into play.
Washington accused Beijing of hiding information and the WHO of having bowed to the will of the Chinese authorities.
Although less critical, other WHO member states suspect Beijing will delay the process.
“We hope – and we have guarantees in this sense – from our Chinese government colleagues that the field part of the mission will be facilitated and carried out as soon as possible, with the aim of reassuring the international community on the quality of the scientific aspect of things” , WHO official Mike Ryan said recently.
Why is origin important?
“Understanding how an epidemic started is essential to prevent new introductions of the virus into the human population,” explains WHO.
The goal is “to understand the mechanism and implement measures to prevent the emergence of a new SARS-CoV-3, 4, etc.”, comments Etienne Simon-Lorière.
These measures would consist in “modifying our forms of contact with animals, the appearance of which is possible”, for example by banning certain types of farming.
At the time of the SARS epidemic in 2002, a ban on the consumption of civets and the closure of farms helped prevent the virus from being reintroduced to humans.
The small mammal consumed in China had been identified as the intermediate host of the coronavirus responsible for the outbreak.
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