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VIENTIANE (BLOOMBERG) – Bats living in limestone caves in northern Laos have been found to carry coronaviruses that share a key characteristic with Sars-CoV-2, bringing scientists closer to determining the cause of Covid -19.
Researchers from the Institut Pasteur de France and the University of Laos have looked for viruses similar to the one that causes Covid-19 among hundreds of horseshoe bats.
They found three with closely matched receptor binding domains – the part of the coronavirus spike protein used to bind to human ACE-2, the enzyme it targets to cause infection.
The discovery, reported in an article published Friday (September 17) which is being considered for publication by the journal Nature, shows that viruses closely related to Sars-CoV-2 exist in nature, including in several Horseshoe Bat, or horseshoe bat, species.
Research supports the hypothesis that the pandemic started from an outburst of a virus transmitted by bats.
About 1,000 of these infections can occur daily in southern China and Southeast Asia in areas with high bat populations in the region. Horseshoe Bat kind, a study revealed Tuesday.
The three viruses found in Laos, named BANAL-52, BANAL-103 and BANAL-236, are “the closest ancestors of Sars-CoV-2 known to date,” said Dr Marc Eloit, head of the discovery pathogens at the Institut Pasteur. in Paris, and co-authors.
“These viruses may have contributed to the origin of Sars-CoV-2 and may inherently pose a future risk of direct transmission to humans.”
The receptor binding domains of three Laos coronaviruses are closer to that of Sars-CoV-2 than to the RaTG13 virus identified in Rhinopholus affinis bats from the Mojiang mine shaft in Yunnan province, which was considered the closest match to the pandemic strain.
The BANAL-236 virus has a receptor binding domain almost identical to the pandemic virus, according to the article.
“The Sars-CoV-2 receptor binding domain looked unusual when it was first discovered because there were so few viruses to compare it to,” said Dr. Edward Holmes, evolutionary biologist at the University of Sydney, which was not involved in the research.
Search for ancestors
“Now that we are taking more samples from nature, we are starting to find these pieces of closely related gene sequences,” Dr Holmes said in an email on Saturday. “Eventually, with more sampling, the natural ancestry of the entire Sars-CoV-2 genome will be revealed.”
None of the bat viruses isolated in Laos harbor a furin cleavage site in the tip that facilitates entry into cells. It is a feature of the Sars-CoV-2 virus that has led some scientists to speculate that it was created in the laboratory.
No evidence to support the theory of laboratory leaks has emerged. Last month, the U.S. intelligence community ruled out the possibility that Sars-CoV-2 was developed by China as a biological weapon, but no consensus was reached on its origin.
The lack of furin cleavage may be explained by insufficient sampling in bats, or by the acquisition of the furin cleavage site during transmission chains in an alternate animal host, or during unreported circulation in humans in the early stages of the outbreak when the virus may have caused few symptoms, the authors said.
“Our results highlight the presence of new bat sarbecoviruses that appear to have the same potential for infecting humans as the early strains of Sars-CoV-2,” they said.
Guanos collectors
People who spend time in or near caves, such as guano collectors, are particularly at risk of exposure.
Further investigation is needed to assess whether people exposed to bats have been infected with any of these viruses and whether they have antibodies that may provide protection against subsequent Sars-CoV-2 infections.
“This article is really interesting and we need more research like this,” Dr Maria Van Kerkhove, World Health Organization technical officer for Covid-19, said in an email.
Researchers studied 645 bats of 46 species captured at four sites – in Fueng and Meth districts of Vientiane province, and Namor and Xay districts in Oudomxay province – between July of the year last and January of this year.
Bats live in the limestone karst terrain common to China, Laos and Vietnam in the Indochina Peninsula.
The article highlights the diversity of Sars-CoV-2-like viruses found in bats in Southeast Asia, Dr Holmes said.
“Continuous sampling is the only way to understand the origins of this virus and it is important that more sampling is done across China as this remains the most likely place of origin,” he said. .
“This study highlights that bat coronaviruses that have the potential to infect humans readily exist in nature and could emerge at any time. This is the clear risk for the future.”
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