AsianScientist (Feb. 18, 2021) – While the beginnings of the COVID-19 pandemic are still murky, scientists have found evidence of coronaviruses related to SARS-CoV-2 in bats and pangolins from Southeast Asia. Their findings, published in Nature Communications, expand the geographical footprint of SARS-CoV-2 related coronaviruses by nearly 5,000 kilometers.
During the 2003 SARS outbreak, coronaviruses 99 percent identical to the circulating SARS-CoV strain were identified in civets. However, until now, the true origins of the SARS-CoV-2 virus responsible for COVID-19 remain elusive.
So far, bat coronavirus strains like RaTG13 and RmYN02 from China bear the closest resemblance to SARS-CoV-2—with the viruses respectively sharing 96 and 93.6 percent of their genomes with SARS-CoV-2. This similarity suggests that the virus emerged from bats, though related coronaviruses have also been reported in pangolins.
To pinpoint SARS-CoV-2’s provenance, Professor Wang Linfa from the National University of Singapore and collaborators from Chulalongkorn University surveyed a colony of Rhinolophus acuminatus bats in Eastern Thailand. The isolated virus, named RacCS203, exhibits 91.5 percent genome similarity to SARS-CoV-2 and is closely related to RmYN02.
Interestingly, a closer look at the RacCS203’s spike protein, which mediates viral entry to human cells, indicates that the strain is unable to use the human ACE2 receptor to enter host cells. According to the authors, this finding suggests that the strain’s spike protein may have undergone recombination. Alternatively, there may be other ways for SARS-CoV-2 related coronaviruses to enter host cells beyond binding to ACE2.
The team also discovered high levels of neutralizing antibodies against SARS-CoV-2 in bats from the study location as well as a pangolin from southern Thailand—providing further proof of SARS-CoV-2-related coronaviruses in the region. Given their findings, Linfa and his collaborators are confident that such coronaviruses are widely present in bats across Asia.
Indeed, aside from China and Thailand, SARS-CoV-2 related coronaviruses have also been detected in Japan’s Iwata Prefecture. Taking all these locations into account, SARS-CoV-2 relatives have been detected within a total distance spanning around 4,800km.
“The current study provides further experimental evidence to support the notion that the distribution of SC2r-CoVs is not limited to China. Southeast Asia, due to its richness in both relevant bat species diversity and population density, may be more likely to be a hotspot for such viruses,” concluded the authors.
Source: Nature; Photo:Shutterstock.
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