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Viruses found in Laos bats are closest known relatives to SARS-CoV-2

Transmission electron micrograph of SARS-CoV-2 virus particles, isolated from a patient. Image captured and color-enhanced at the NIAID Integrated Research Facility (IRF) in Fort Detrick, Maryland. Source - National Institute of Allergy and Infectious Diseases (NIAID) CC SA 2.0.
Transmission electron micrograph of SARS-CoV-2 virus particles, isolated from a patient. Image captured and color-enhanced at the NIAID Integrated Research Facility (IRF) in Fort Detrick, Maryland. Source - National Institute of Allergy and Infectious Diseases (NIAID) CC SA 2.0.

Scientists have discovered another clue to the origins of the virus that causes Covid-19, with bats living in caves in Laos found to be carrying a similar pathogen that experts suggest could potentially infect humans directly.

Researchers from the Pasteur Institute in France and the University of Laos captured 645 bats from limestone caves in northern Laos and screened them for viruses related to SARS-CoV-2. What they found gives credence to the reports that the virus behind COVID-19 has a natural origin.

According to their study, posted to the preprint server Research Square on Sept. 17, among the hundreds of bats tested in Vientiane Province, three were found to carry viruses that closely resemble the virus that causes Covid-19, particularly in the mechanism for latching on to human cells.

In three horseshoe (Rhinolophus) bat species, they found viruses that are each more than 95 percent identical to SARS-CoV-2, which they named BANAL-52, BANAL-103, and BANAL-236.

Bats with Covid-like viruses found in Laos: study
Researchers said their findings show that viruses genetically close to the SAR-CoV-2 pandemic virus ‘exist in nature’ among bat species – Copyright GETTY IMAGES NORTH AMERICA/AFP/File Ethan Miller

The new viruses contain receptor binding domains that are almost identical to that of SARS-CoV-2, and can therefore infect human cells. The receptor-binding domain allows SARS-CoV-2 to attach to a receptor called ACE2 on the surface of human cells to enter them.

“The idea was to try to identify the origin of this pandemic,” Marc Eloit, who leads the Pasteur Institute’s pathogen discovery laboratory, told AFP. Eloit, whose team analyzed the samples collected, said there were still key differences between the viruses found and SARS-CoV-2.

Case for natural origin

“When SARS-CoV-2 was first sequenced, the receptor-binding domain didn’t really look like anything we’d seen before,” says Edward Holmes, a virologist at the University of Sydney in Australia. This caused some people to speculate that the virus had been created in a laboratory. But the Laos coronaviruses confirm these parts of SARS-CoV-2 exist in nature, he says.

“I am more convinced than ever that SARS-CoV-2 has a natural origin,” agrees Linfa Wang, a virologist at Duke–NUS Medical School in Singapore.

Chinese scientists find a new batch of coronaviruses in bats
There are 106 species of Horseshoe bats in the world. This image is of a lesser Horseshoe Bat (Rhinolophus hipposideros) Image – F. C. Robiller / naturlichter.de BCC SA 3.0

Alice Latinne, an evolutionary biologist at the Wildlife Conservation Society Vietnam in Hanoi, says that added to recent studies of relatives of SARS-CoV-2 discovered in Thailand, Cambodia, and Yunnan in southern China, this latest study demonstrates that southeast Asia is a “hotspot of diversity for SARS-CoV-2 related viruses.”

It seems that the more scientists learn about the many close relatives of the SARS-CoV-2 virus, the more intriguing and dangerous the viruses become. Last year, researchers described another close relative of SARS-CoV-2, called RaTG13, which was found in bats in Yunnan. It is 96.1 percent identical to SARS-CoV-2 overall and the two viruses probably shared a common ancestor 40–70 years ago.

BANAL-52 is 96.8 percent identical to SARS-CoV-2, says Eloit — and all three newly discovered viruses have individual sections that are more similar to sections of SARS CoV-2 than seen in any other viruses.

Viruses swap chunks of RNA with one another through a process called recombination, and one section in BANAL-103 and BANAL-52 could have shared an ancestor with sections of SARS-CoV-2 less than a decade ago, says Spyros Lytras, an evolutionary virologist at the University of Glasgow. “These viruses recombine so much that different bits of the genome have different evolutionary histories,” he says.

The authors say their findings support the hypothesis that SARS-CoV-2 resulted from the recombination of viral sequences existing in horseshoe bats. The findings are currently being considered for publication in a Nature journal, Bloomberg reported.

Written By

Karen Graham is Digital Journal's Editor-at-Large for environmental news. Karen's view of what is happening in our world is colored by her love of history and how the past influences events taking place today. Her belief in man's part in the care of the planet and our environment has led her to focus on the need for action in dealing with climate change. It was said by Geoffrey C. Ward, "Journalism is merely history's first draft." Everyone who writes about what is happening today is indeed, writing a small part of our history.

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