Virus responsible for the Covid-19 pandemic has been circulating in bats for up to 70 YEARS, study suggests
- Scientists say the virus could have first evolved in horseshoe bats in 1948
- Say pangolins are likely not the intermediary host between bats and humans
- Claim the SARS-CoV-2 virus has been in circulation in bats for decades
- Warn that this means various other coronaviruses capable of infecting humans could be lurking in some bat species
The coronavirus causing the current pandemic which has killed more than 650,000 people around the world may have first evolved in bats in 1948, a study claims.
Academics made the discovery as part of a research project investigating the ancestral origins of the SARS-CoV-2 virus, which causes Covid-19.
Scientists led by the Pennsylvania State University compared the Covid-causing pathogen to its closest relatives found in bats.
Previous research has identified horseshoe bats as a reservoir of coronaviruses and the likely original source of SARS-CoV-2.
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Previous research has identified horseshoe bats as a reservoir of coronaviruses and the likely original source of SARS-CoV-2. It is now thought the virus was circulating in the animals for decades (stock)
Tracking the evolution of the virus through time is difficult, as coronaviruses often share genetic information and mutate in a process called recombination.
However, researchers found three sections of the virus’s genetic information, which appear to have been left untouched by recombination.
Analysis of these sections reveals SARS-CoV-2 and its closest relative in bats, called RaTG13, share a common ancestor.
The question remains as to when the deadly SARS-CoV-2 split from all the other coronaviruses, which live in ‘endemic equilibrium with their natural host species, horseshoe bats’.
SARS-CoV-2, the virus which causes Covid-19, evolved after several different coronaviruses merged into one, a study has found.
Scientists came to the conclusion while trying to understand the evolutionary history of the coronavirus in a bid to help make a vaccine.
High-resolution images reveal the spike on the surface of SARS-CoV-2 is 97 per cent identical to the spike on the coronavirus it most closely resembles, called RaTG13, which is found in bats.
However, the slight differences make SARS-CoV-2 far more stable and 1,000 times better at latching on to a receptor on human cells, called ACE2, a study reveals.
ACE2 has been called the ‘entry key’ to the human body and the mutations on the spike of SARS-CoV-2 make it a perfect fit.
The researchers from the Francis Crick Institute in London say their finding does not help clarify the origin of the virus which has killed more than half a million people.
But this latest research does indicate the virus evolved over time naturally, and was not man-made.
China has repeatedly fended off accusations that the coronavirus was created in a lab in the city of Wuhan, where the pandemic began in December.
And World Health Organization officials have disputed the claims multiple times, saying there is no evidence the new coronavirus was created in a laboratory.
Because the scientists studied three sections of DNA, they got three different dates for when the virus diverged from its ancestral lineage of sarbecoviruses, the subgroup of coronavirus to which SARS-CoV-2 belongs.
These dates were 1948, 1969 and 1982, ‘indicating that the lineage giving rise to SARS-CoV-2 has been circulating unnoticed in bats for decades’, the researchers write in their study, published in Nature Microbiology.
It also found that SARS-CoV-2 is 96 per cent similar to RaTG13 which was found in a bat in 2013 and diverged from this sister strand in 1969.
The researchers warn that the virus has existed for between 40 and 70 years and therefore bats may well contain other coronaviruses which can infect humans.
As well as looking at how long the virus dates back in bats, the researchers tried to clear up the murky picture as to how it entered humans.
It is known from previous studies that the virus enters humans thanks to a specific site on the virus’s surface spike, known as a receptor-binding domain (RBD).
This allows the spike of the virus to latch on to the ACE2 receptor on human cells and unlocks the body’s defences, allowing the virus to wreak havoc.
However, of the dozens of coronaviruses previously identified in bats, not a single other sarbecovirus has been found with the unique RBD, not even RaTG13.
The nearest thing to the RBD of SARS-CoV-2 on other viruses is seen in pangolins.
Previously, this fact had been used to incriminate pangolins as the intermediary host which acted as a stepping stone in allowing the virus to hop from bats to humans.
But according to the latest research, that is unlikely.
Instead, pangolins are in the same boat as humans and RaTG13 did have the ability to infect humans when the two viruses diverged.
However, after the two viruses split, RaTG13 then likely mutated and nullified its ability to infect human cells.
Scientists led by the Pennsylvania State University compared the Covid-causing pathogen to its closest relatives found in horseshoe bats (pictured). Study found it may have first evolved in 1948
David L Robertson, professor of computational virology at the MRC-University of Glasgow Centre for Virus Research, said: ‘SARS-CoV-2’s receptor-binding domain sequence has so far only been found in a few pangolin viruses.
‘While it is possible that pangolins may have acted as an intermediate host facilitating transmission of SARS-CoV-2 to humans, no evidence exists to suggest that pangolin infection is a requirement for bat viruses to cross into humans.
‘Instead, our research suggests that SARS-CoV-2 likely evolved the ability to replicate in the upper respiratory tract of both humans and pangolins.’
Four ‘sister’ species of the horseshoe bat that sparked the global coronavirus pandemic are discovered
Four relatives of the bat species thought to be the original source of the novel coronavirus have been found in Africa.
The previously undiscovered animals are considered to be ‘sister’ species to the horseshoe bat, which is widely believed to be the origin of the SARS-CoV-2 virus which has caused the COVID-19 pandemic.
Bats act as reservoirs to coronaviruses and are immune to them but have the ability to spread them.
Researchers say that studying the four new species and the viruses they harbour could help scientists and medics to prepare for any future outbreaks.
Professor Mark Pagel from the University of Reading, who was not involved in the study, says pangolins were suspected due to their popularity in wet markets as sources of materials for traditional medicine.
‘The variable loop region of the important spike protein [in pangolins] is more closely related to SARS-CoV-2 than is the variable loop region of RaTG13,’ he says.
‘The authors’ analysis shows that the difference between RaTG13 and SARS-CoV-2 in the critical variable loop region probably arose in RaTG13 after it separated from the common ancestor.
‘This then points to the conclusion that there are as yet undetected horseshoe bat viruses that are the likely source of Covid-19 — ones that have not been altered like RaTG13 has.’
The academics say that this study again highlights the dangers posed by zoonotic diseases, where a pathogen jumps from one species to another.
Bats have evolved over centuries to live unaffected by dozens of coronaviruses, but any number of them could be fatal and highly infectious to humans.
Maciej Boni, associate professor of biology at Penn State, warns the Covid-19 pandemic ‘will not be our last’.
He said: ‘Coronaviruses have genetic material that is highly recombinant, meaning different regions of the virus’s genome can be derived from multiple sources.
‘This has made it difficult to reconstruct SARS-CoV-2’s origins – you have to identify all the regions that have been recombining and trace their histories.
‘We put together a diverse team with expertise in recombination, phylogenetic dating, virus sampling, and molecular and viral evolution.’
He added: ‘We were too late in responding to the initial SARS-CoV-2 outbreak but this will not be our last coronavirus pandemic.
‘A much more comprehensive and real-time surveillance system needs to be put in place to catch viruses like this when case numbers are still in the double digits.’
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