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- Many theories exist around the origins of the SARS-CoV-2 virus, which causes COVID-19, but none have yet been proven.
- Parts of the SARS-CoV-2 virus genome are
so unusual that it gave rise to conspiracy theories that the virus must have been developed in a lab. - Researchers have now discovered among bats living in caves in Laos virus strains so similar to SARS-CoV-2 that they think they can infect humans.
- This finding could prove the natural origins of the COVID-19 pandemic and that direct transmission of the bat virus to humans is a possible cause of the pandemic.
Since SARS-CoV-2, the virus that causes COVID-19, was first detected in Wuhan, China in December 2019, global efforts have been made to determine its origins.
As the pandemic was believed to originate from Wuhan, a lot of effort has focused on China, assuming that since the virus was first detected there, it likely started there.
Now two articles under review by the journal Nature and published as preprints cast doubt on these assumptions and indicate that to uncover the origins of the virus, researchers may need to look further.
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One of the reasons SARS-CoV-2 is so infectious is a region on its spike protein that gives it the ability to bind to a receptor found on the surface of many human cells called ACE2.
In an article submitted to Nature, researchers from the Institut Pasteur in Paris, France, and Laos have now reported finding viruses with receptor binding domains very similar to those found on SARS-CoV-2 in cave bats north of Laos.
The researchers took blood, saliva, anal feces and urine samples from 645 bats of 46 different species found in limestone caves in northern Laos, near the southwestern border of China.
They discovered three distinct viral strains in three different species of the Rhinolophus bat, commonly known as the horseshoe bat. RNA sequencing revealed that these viruses were over 95% identical to SARS-CoV-2, and one, the virus closest to SARS-CoV-2 found so far, was similar to 96.8%.
Further experiments showed that the receptor binding domain of viruses had a high affinity for human ACE2 receptors. This was comparable to the affinity of the strains of SARS-CoV-2 that scientists discovered at the start of the pandemic, suggesting that these viruses could directly infect humans.
Last year, scientists detected a similar virus in Yunnan in southwest China. It was 96.1% similar to SARS-CoV-2, which means that this article describes the closest virus detected to date.
Professor Edward Holmes of the University of Sydney, Australia, who has studied the emergence and spread of SARS-CoV-2 but was not involved in this research, said Medical News Today the paper was “really important”.
“In my opinion, these viruses will not only be found in bats and pangolins. Ecology is not like that. I suspect they will be found in other mammalian species as well, but have not yet been sampled, ”Professor Holmes said.
“Some of these Laotian viruses are extremely close to SARS-CoV-2 in the key receptor binding domain (part of the spike protein) of the virus. This means that the functional core of the virus exists in nature, so there is no need to think that the virus was somehow created or adapted in a lab. “
– Prof. Edward Holmes
Further doubt has been cast on the hypothesis that the virus responsible for the COVID-19 pandemic originated in Wuhan with another preprint submitted to Nature.
A study by a team from the Chinese Academy of Medical Sciences and the Beijing Union Medical College in Beijing suggested that viruses linked to SARS-CoV-2 are “extremely rare” in bats in China , after taking nasal and anal swabs from more than 13,000 bats. between 2016 and 2021 in 703 locations across the country.
The document also showed that SARS-CoV-2 was undetectable in samples taken from the Wuhan Huanan market, 40 days after the market closed, which was due to fears that the initial infection event might occur. is produced there.
The authors conclude that more research should be done in southern and southwestern China to determine whether the SARS-CoV-2 virus originated there.
One of the reasons it has been so difficult to establish the origin of the coronavirus is the viral genomes that change through a process called recombination, rather than just mutations. Viral recombination occurs when two different strains infect the same host cell.
Since they replicate in the same cell, they can interact, and the viral progeny they generate can have genes from both parents. This can make it difficult to establish the lineage of this virus.
“Recombination appears to be important for the overall evolution of these viruses,” said Spyros Lytras, evolutionary virologist at the University of Glasgow in the UK. MNT.
“So basically we’re saying these viruses are changing pieces of their genome all the time, and the new viruses from Laos are really showing that. Although [these viruses] are in the same place, basically the same cave, they all have different pieces of their genome that have different combinations of recombinant parts.
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