Closest known relatives of virus behind COVID-19 found in Laos
Studies of bats in China and Laos show southeast Asia is a hotspot for potentially dangerous viruses similar to SARS-CoV-2.
Scientists have found three viruses in bats in Laos that are more similar to SARS-CoV-2 than any known viruses. Researchers say that parts of their genetic code bolster claims that the virus behind COVID-19 has a natural origin — but their discovery also raises fears that there are numerous coronaviruses with the potential to infect people.
David Robertson, a virologist at the University of Glasgow, UK, calls the find “fascinating, and quite terrifying”.
The results, which are not peer reviewed, have been posted on the preprint server Research Square1. Particularly concerning is that 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.
To make the discovery, Marc Eloit, a virologist at the Pasteur Institute in Paris and his colleagues in France and Laos, took saliva, faeces and urine samples from 645 bats in caves in northern Laos. In three horseshoe (Rhinolophus) bat species, they found viruses that are each more than 95% identical to SARS-CoV-2, which they named BANAL-52, BANAL-103 and BANAL-236.
“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.
Together with relatives of SARS-CoV-2 discovered in Thailand2, Cambodia3 and Yunnan in southern China4, the study demonstrates that southeast Asia is a “hotspot of diversity for SARS-CoV-2 related viruses”, says Alice Latinne, an evolutionary biologist at the Wildlife Conservation Society Vietnam in Hanoi.
In an extra step in their study, Eloit and his team showed in the laboratory that the receptor binding domains of these viruses could attach to the ACE2 receptor on human cells as efficiently as some early variants of SARS-CoV-2. The researchers also cultured BANAL-236 in cells, which Eloit says they will now use to study how pathogenic the virus is in animal models.