The conclusions of this work, in open access since Wednesday on the scientific platform Research Arena, should remain the subject of peer review with a view to publication in a scientific journal.
In order to better understand the evolution and origins of SARS-CoV-2, which has been the subject of intense speculation for months, researchers from the Pasteur Institute in Paris, the Pasteur Institute in Laos and the National University of Laos led the end of 2020 and the beginning of 2021 a field mission in the north of the country with different species of bats. Live in limestone caves.
“The initial idea was to try to determine the origin of this epidemic,” explains Marc Elwett, head of the “Pathogen Detection” laboratory at the Pasteur Institute in Paris, whose teams analyzed the various samples collected. “For various reasons accumulating, it is suspected that some insect-eating bats could be the reservoir of the virus.”
The samples were taken in an area that is part of a massive karst topography, and geological formations consisting mainly of limestone, which also include northern Vietnam and southern China.
“Laos shares this common area with southern China, which is full of cavities where bats live, hence the idea to go there,” continues Mark Elwett. Because what happens there is a representative of this ecosystem.
Conclusions of the Pasteur Institute analyzes: The sequence of the virus in bats is almost identical to that of the SARS-CoV-2 virus, and the researchers were able to demonstrate their ability to allow the viruses to enter human cells.
However, the viruses studied lack the “furin site” found in SARS-CoV-2, a function that activates the so-called spike protein by allowing the virus to better enter human cells and the presence of which limits the potency of the virus’ pathogen.
Mark Elwett says that several hypotheses could explain this missing link. He asserts, for example, that “a non-pathogenic virus may have first circulated in humans before it mutated.” “Or a virus very close to the viruses that have been identified that has this fizz site, but we haven’t found it yet.”
Another question: “How did the bat virus found in caves get to Wuhan,” in China, the known starting point of the epidemic, 2,000 kilometers away? No answer at the moment.
In any case, this study is “a significant advance in determining the origin of SARS-CoV-2,” Mr. Elwett said.
The main conclusion that may be is that there are viruses very close to SARS-CoV-2 in bats that are able to infect humans without an intermediate animal, such as pangolins.
At the end of August, experts from the World Health Organization, author of a report on the origin of Covid, warned that research was “off” on the topic.
They were part of a team of 17 international experts appointed by the World Health Organization and 17 Chinese experts, whose report was published on March 29, following an investigation conducted in January in Wuhan.
Without providing a clear answer, this report listed four more or less likely scenarios. Most likely, the virus was transmitted to humans through an animal infected with a bat.
Then came the hypothesis of direct transmission without an intermediate animal, transmission through food, particularly frozen meat, and finally an accidental laboratory leak, although considered “highly unlikely”.
Since then, the experts noted, “no data” supporting the “lab leak hypothesis” has been published or submitted to the World Health Organization.