A year and a half after its onset, the origin of the pandemic is still the subject of much speculation. But little by little, the pieces of the puzzle are trying to fall into place. On the question of the origins of Covid-19, “a major breakthrough” could have been discovered. In fact, researchers from the Institut Pasteur have identified viruses similar to Sars-CoV-2 in bats in northern Laos, capable of infecting humans. The conclusions of this work, in open access since Wednesday on the scientific platform “Research Square“, have yet to be peer reviewed for publication in a scientific journal.
In order to better understand the evolution of Sars-CoV-2 and its origins, researchers from the Institut Pasteur in Paris, the Institut Pasteur in Laos and the National University of Laos have decided to join forces to lead at the end of 2020 and the beginning of 2021 a field mission in the north of the country with different species of bats living in limestone caves. In total, 645 bats were studied. “The initial idea was to try to identify the origin of this epidemic”, explains to AFP Marc Eloit, head of the “discovery of pathogens” laboratory at the Institute. Pasteur in Paris, whose teams analyzed the various samples collected.
“For various reasons which accumulate, it is suspected that certain insectivorous bats could be the reservoir of the virus”. The samples took place in an area that is part of an immense karstic relief, geological formations mainly made up of limestone, which also encompasses northern Vietnam and southern China. “Laos shares this common territory with southern China, filled with cavities where bats live, hence the idea of going there,” continues Marc Eloit. Because what happens there is representative of this ecosystem. And the conclusions of the Institut Pasteur analyzes are as follows: the virus sequences found in bats are almost identical to those of Sars-CoV-2 and the researchers were able to demonstrate their ability to allow viruses to enter. in human cells.
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A serious lead and various questions
“These three coronaviruses close to Sars-Cov-2 have a domain called RBD, located on the Spike protein, which makes it possible to bind to human cells. Of the 17 functionally important amino acids in this domain, there are only ‘one or two that differ from those of Sars-Cov-2 “, further details Marc Eloit, to our colleagues from HuffPost. However, the viruses studied lacked the “furin site” present in Sars-CoV-2, a function which activates the so-called Spike protein by allowing the virus to better enter human cells and whose existence conditions the power. pathogen of the virus.
In other words, if these coronaviruses can be transmitted to humans, it is not said that they can harm us. And several hypotheses could explain this missing link, advances Marc Eloit. “Perhaps a non-pathogenic virus first circulated in humans before mutating,” he emphasizes, for example. “Or a virus very close to the identified viruses has this furinous site, but we have not yet found it”.
“A major breakthrough”
If the question of the origin of the virus remains open, this work makes it possible to whitewash the pangolin, accused at the start of the pandemic of having infected humans. But another question remains: “how did the bat virus found in caves get to Wuhan”, in China, the known starting point of the pandemic, 2000 kilometers away? No answer for the moment.
Anyway, this study “is a major advance in the identification of the origin of Sars-CoV-2”, believes Marc Eloit. The main conclusion of which would be that there are viruses very close to Sars-CoV-2 in bats capable of infecting humans without an intermediate animal. At the end of August, WHO experts, authors of a report on the origin of the Covid, warned that research was “at a standstill” on this subject.
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They were part of a team of 17 international experts appointed by the WHO and 17 Chinese experts, whose report was published on March 29, after an investigation conducted in January in Wuhan. Without providing a clear answer, this report listed four more or less probable scenarios. The one considered most likely was transmission of the virus to humans through an animal infected with a bat. Then came the hypotheses of a direct transmission without an intermediate animal, of a transmission through food, in particular frozen meat, and finally of an accidental laboratory leak, however deemed “extremely improbable”. Since then, “no data” supporting “the hypothesis of a laboratory leak has been neither published nor submitted to the WHO”, noted the experts.