Sayak Banerjee, Amity University Kolkata
Researchers in Japan and Cambodia have discovered coronaviruses which is similar to COVID-19. These are the first known relatives of SARS-Cov-2 to be found outside China and to be originated from horseshoe bats or Rhinolophus bats. It is still unknown if COVID-19 was transferred directly from bats to people or indirectly by an intermediate host. A virologist in Cambodia said that the virus could help them know the origin of the pandemic by providing vital data regarding how it was passed from bats to people. For such apprehensions, the virus must share 97% of its genome with COVID-19, whereas it shares 81% of its genome, thus making it too distant to apprehend the origin of the pandemic.
RaTG13 being the closest among the few known relatives of SARS-CoV-2 was found in intermediate horseshoe bats (Rhinolophus affinis) in Yunnan in 2013 including various other Rhinolophus bats found between 2015 to 2019. COVID-19 was not a novel virus that appeared all of a sudden as viruses associated with COVID-19 existed before it came to spotlight. Preliminary genome sequencing of a small fragment of the new bat virus, in Shamel’s horseshoe bats (Rhinolophus shameli) from Cambodia, proved the similarity of the same region in SARS-CoV-2 and RaTG-13, indicating a close relationship between the three and this region is highly conserved in coronaviruses. On sequencing 70% of the new virus’s genome, the Cambodia team found that some of the essential components of the virus were absent. These include the genes that encode for the spike protein which is generally used by coronaviruses to invade other cells.
Although the genomes of RaTG13 and SARS-CoV-2 vary by only 4%, since a common ancestor is shared by them, the difference constitutes between 40 and 70 years of evolution. The newly discovered Rc-o319, found in little Japanese horseshoe bats (Rhinolophus cornutus) appeared to have a distant relation because the virus is unable to bind to the receptor that is used by SARS-CoV-2 to enter human cells, implying that it could not easily infect people. Most importantly, being distantly related, it would aid the scientists to comprehend the diversity of the virus family. One of the scientists said that they expect that one or more of these viruses to be found will be so much similar to COVID-19 that it can be considered as the true ancestor.
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Source: Murakami S, Kitamura T, Suzuki J, et al. Detection and Characterization of Bat Sarbecovirus Phylogenetically Related to SARS-CoV-2, Japan. Emerging Infectious Diseases. 2020;26(12):3025-3029. doi:10.3201/eid2612.203386. https://doi.org/10.3201/eid2612.203386
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