THE origins of the virus responsible for Covid-19 have been "unambiguously" traced to horseshoe bats, according to Scottish scientists.

But the Glasgow-led team say "dramatically more wildlife sampling" is needed to pinpoint the creature that ultimately passed the virus to humans.

And they warn that there is "undoubtedly" a virus highly related to SARS-CoV-2 still present somewhere in the wild.

The conclusions follow in-depth work by the MRC-University of Glasgow Centre for Virus Research, which looked at the evolutionary history of bat coronaviruses related to SARS-CoV-2, the virus responsible for Covid-19.

The National: Lesser horseshoe batsLesser horseshoe bats

It also looked at the phenomenon of virus recombination, which occurs when a host is infected with two coronaviruses at once and the viruses swap elements of their genetic material inside host cells to create a new "recombinant" health danger.

SARS-related coronaviruses, which include SARS-CoV-2, are dispersed over a large geographical area across China and South East Asia.

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By tracing the recombinant sequence patterns, scientists concluded that there has been relatively recent geographic movement and co-circulation of these viruses' ancestors, extending across the ranges covered by their bat hosts in China and South East Asia over the last century.

The study concluded that the origin of SARS-CoV-2 "can be unambiguously traced to horseshoe bats, genus Rhinolophus."

However, a "direct proximal ancestor" to SARS-CoV-2 has not yet been found, since the closest known relatives collected in Yunnan shared a common ancestor with SARS-CoV-2 around four decades ago.

Professor David L Robertson, senior author on the study, said: "Our analysis highlights the need for dramatically more wildlife sampling to pinpoint the exact origins of SARS-CoV-2 and understand more fully the risk of infection of humans by viruses like these across China and South East Asia."

Spyros Lytras, first author of the study said: "Recombination is a mechanism seen in many viruses, where related viruses can swap bits of their genetic material when they find themselves infecting the same cell, resulting in a new mosaic virus.

"It is clear that recombination is a defining feature of SARS-related coronaviruses and essential to account for when examining the viruses' evolution."

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But the scientists said many questions remain.

The research paper stated: "An urgent question relating to the prevention of another emergence, is where in China or South East Asia is the SARS-CoV-2 progenitor located (our analysis shows this is not necessarily Yunnan); which bat or other animal species are harbouring sarbecoviruses and linked to this what is the risk of future spillover events?

"There is undoubtedly a virus highly related to SARS-CoV-2 still present somewhere in the wild.

"The best we can do is maximise the probability that future sampling efforts will uncover that host species or sub-species."

The study is published in Genome Biology and Evolution.