A new Covid-like virus with the potential to jump to humans and livestock has been identified in bats in southern China, according to new research.
Chinese and Australian scientists took samples from 149 bats across Yunnan province, which borders Laos and Myanmar, and identified five viruses “likely to be pathogenic to humans or livestock”.
Among them was a bat coronavirus closely related to both Sars-Cov-2 and Sars.
“This means that Sars-Cov-2-like viruses are still circulating in Chinese bats and continue to pose an emergence risk,” said Prof Eddie Holmes, an evolutionary biologist and virologist at the University of Sydney and co-author of the report.
The research – which was published as a pre-print and has not yet been peer-reviewed – showed that bats were regularly infected with several viruses simultaneously.
This is significant because it demonstrates the potential for existing viruses to swap bits of their genetic code – a process known as recombination – to form new pathogens.
“The main take-home message is that individual bats can harbour a plethora of different virus species, occasionally playing host to them at the same time,” said Prof Jonathan Ball, a virologist at the University of Nottingham who was not involved in the research.
“Such co-infections, especially with related viruses like coronavirus, give the virus opportunity to swap critical pieces of genetic information, naturally giving rise to new variants,” he said.
‘Clear and present threat’
Professor Stuart Neil, head of the department of infectious diseases at King’s College London, added: “This study gives us a very important snapshot into the evolution and ecology of [coronaviruses], the scope for them to recombine and skip into new species regularly.”
It shows a “clear and present threat of new spillovers to humans,” he added.
Previously, analysis has estimated that as many as 400,000 people are infected by viruses carried by bats every year across southern China and southeast Asia.
Of the five viruses labelled “viruses of concern”, one – known as BtSY2 – had characteristics of both Sars, a virus which killed 774 people and infected 8,000 in an outbreak in 2003, and Sars-Cov-2, which causes Covid-19 disease.
Of note, BtSY2 had a receptor binding domain – the part of the spike protein that it uses to latch onto human cells, which most Covid-19 vaccines target – very similar to Sars-Cov-2, possibly closest seen in animal viruses to date. This suggests BtSY2 may also be able to infect humans.
“It’s as close as the BANAL bat viruses from Laos, and the closest animal virus we’ve seen from China,” said Prof Holmes, referring to the most similar virus to Sars-Cov-2 detected in nature, which was found in bat caves in Laos last year.
The latest pre-print does not explain how Sars-Cov-2 initially jumped to humans, nor does it rule out a laboratory-related accident, but it does help scientists track the potential evolution of the virus.
It comes after a new analysis, presented at the One Health Congress in Singapore earlier this month, suggested that some bat coronaviruses shared a common ancestor with Sars-Cov-2 as recently as 2016, by comparing chunks of coronavirus genomes.
“We need to sequence the entire viral genome of these circulating bat viruses, not just tiny pieces of it [because they mutate and recombine constantly],” said Prof Joel Wertheim, an evolutionary biologist at the University of California San Diego and co-author of the analysis.
“If we don’t sequence small pieces of these bat virus genomes, we may miss the important bits that reveal the pre-history of Sars-CoV-2.”
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