Coronaviruses, which can infect humans, bats have been able to circulate unnoticed for decades.
Studies show that one of the closest ancestors of the virus that causes Covid-19 appeared in bats between the ages of 40 and 70.
Scientists said he had been ready for human crossbreeding for some time.
They further question conspiracy theories that the virus that caused Covid-19 was bioengineered or escaped the lab, they added.
The study was published by David Robertson, a professor at the University of Glasgow, in the journal Nature Microbiology.
He said that although Sars-CoV-2 (a pandemic coronavirus) is genetically very close to the nearest known bat viruses, they have been isolated for decades.
“This shows that these viruses, which can occur in humans, have been around for some time,” he told BBC News.
“We really need to understand where or how the virus has entered the human population. If we now believe this bat is spreading like a global virus, we need to monitor it better.”
He stressed the need to continue to monitor emerging human diseases and to take more samples from wild bat populations to prevent future pandemics.
“If these viruses have been around for decades, it means that they have had many opportunities to find new species of hosts,” said prof. Robertson.
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The researchers compared the Sars-CoV-2 genetic model with a closely related bat, a virus called RaTG13.
They discovered both ancestors, but went their own evolutionary paths a few decades ago.
Prof. did not participate in the study. Mark Pagel of the University of Reading said the work showed that coronaviruses that could infect humans existed in bats for maybe 40-70 years, but went unnoticed.
“This is significant in terms of the scale and nature of the problems caused by the transmission of zoonoses to humans – there may be many as yet undetectable viruses that can infect humans living in animal hosts.”
Viruses could infect other wildlife, especially those in close contact with each other through wildlife trafficking.
Previous studies suggest that pangolins may have influenced the evolution of Sars-CoV-2, but a recent study suggests that this is not the case.
Instead, pangolins may have collected the virus more recently, transporting wildlife through contact with other wildlife.
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