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Since the start of the pandemic, researchers around the world have been trying to discover the exact origin of the new coronavirus. In addition to the true “patient 0”, an attempt is made to identify the first or at least the first animal to be infected with this variant of the coronavirus. But also the question is to know which animal was really the first vector of transmission to humans. In this research, and for the first time, close relatives of the novel coronavirus were found outside of China. Scientists found the two viruses in frozen bats and bat droppings stored in Cambodian and Japanese laboratories.
SARS-CoV-2 continues to circulate around the world, now with over 60 million infections and over 1.4 million deaths. Like its cousin, SARS-CoV, which caused severe acute respiratory syndrome (SARS) outbreaks in the early 2000s, SARS-CoV-2 likely came from a bat of the genus Rhinolophus, although some evidence suggests the virus may having infected another animal before infecting humans.
By researching closely related coronaviruses, scientists can help unravel the mystery of how SARS CoV-2 passed from bats to humans, triggering the current pandemic. Recently, virologists said Nature news of having discovered such a virus in Cambodia.
” This is what we were looking for and we found it He said Nature news Dr Veasna Duong, a virologist at the Institut Pasteur du Cambodge in Phnom Penh, who led the research. ” It was thrilling and surprising That is to say, the study is still ongoing and has not yet been published in a scientific journal.
The team discovered the virus in two Shamel’s ‘horseshoe bats’ (R. shameli), which were first caught in 2010, frozen and stored. To confirm the virus’ relationship with SARS-CoV-2, the scientists enlarged a small segment of its genome. This segment, made up of 324 base pairs – the building blocks of RNA – is very similar in known members of the coronavirus family, he said. Nature news Alice Latinne, an evolutionary biologist with the Wildlife Conservation Society Vietnam in Hanoi, who was not involved in the study. ” This segment is often used to differentiate new coronaviruses from known coronaviruses, using subtle differences in its code »He explains.
Sequencing still incomplete
The team found that the new virus’ short segment resembled that of SARS-CoV-2, as well as that of its known closest relative, a coronavirus bat called RaTG13. The team must now sequence the entire genome of the new virus, which likely contains around 30,000 base pairs, to find out exactly how closely it is related to SARS-CoV-2. So far, the team has sequenced around 70% of the genome, but critical genes have yet to be analyzed, including those that contain instructions for building the spike protein that allows the virus to enter cells.
RaTG13, the closest known relative of SARS-CoV-2 to date, shares 96% of its genome with the pandemic virus and likely diverged from the common ancestor of the pathogens between 40 and 70 years ago. So, if the newly discovered virus is at least 97% similar to SARS CoV-2, it would replace RaTG13 as the closest known relative. If the sequences are at least 99% similar, the new virus could be a direct ancestor of the pandemic pathogen, he said. Nature news Aaron Irving, an infectious disease researcher at Zhejiang University in Hangzhou, China.
On the other hand, the new virus may not even resemble SARS-CoV-2 as much as RaTG13. For example, a coronavirus recently discovered in frozen bat droppings in Japan shares about 81 percent of its genome with SARS-CoV-2, according to a study published Nov.2 in the journal Emerging infectious diseases. ” This makes it too distant to give any indication of the origin of the pandemic », Explains Edward Holmes, a virologist at the University of Sydney in Australia. This is because this virus, called Rc-o319, cannot even enter human cells using the same receptor as SARS-CoV-2, according to cell culture studies.
The question of whether the virus found in Cambodia can infect human cells remains unanswered for the time being, pending complete sequencing. However, the discovery of novel coronaviruses in R. shameli bats could give us clues as to how SARS-CoV-2 might have passed to humans and help us anticipate them. future pandemics.
Other coronaviruses linked to SARS-CoV-2 likely exist in Rhinolophus bat populations, which live throughout the region, Holmes explains. ” It is hoped that one or more of these coronaviruses are so closely related to SARS CoV-2 that we can consider it the true ancestor. He concludes.
Source: Nature News
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