By Alexandre Hassanin, Philippe Grandcolas and Géraldine Veron
The origin of the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), aka the 2019-novel Coronavirus, is an issue that concerns scientists and the general public worldwide. In a recent paper, published in Mammalia, a group of French researchers reviewed the available scientific data for sarbecoviruses – a group of viruses that includes SARS-CoV (related to the SARS outbreak in 2002-2003) and the recently spreading SARS-CoV-2. Their aim was to develop hypotheses in regard to the outbreak of Covid-19 in Wuhan, China.
According to the authors, present evidence indicates that bats of the genus Rhinolophus – commonly known as horseshoe bats – are a natural reservoir of all sarbecoviruses. Furthermore, two divergent SARS-CoV-2-like viruses have circulated in southern China (at least in the provinces Guangxi and Guangdong) between August 2017 and March 2019 in captive Sunda pangolins destined for sale at wildlife markets. The researchers consider a direct transmission of the coronavirus from horseshoe bats to humans as well as an indirect transmission via pangolins or other species (with wild or captive animals possibly infecting each other) as valid possibilities.
(Cross-species) infection at wet markets?
The researchers also performed a genetic analysis of seven seized pangolins by using mitochondrial DNA sequences from the public repository SRA data. Each pangolin carried the same SARS-CoV-2-like virus. Based on the animals’ genetic fingerprints, the researchers inferred that the seven individuals were captured in different regions of Southeast Asia.
According to the researchers, this could imply that some pangolins were infected in captivity (by other pangolins or by another species to be determined) suggesting that illegal trade of living wild mammals is at the origin of the Covid-19 outbreak. “However”, they add, “to validate this hypothesis, it is necessary to discover a virus almost identical to SARS CoV-2 in animals sold in wet markets. Although pangolins are good candidates, other mammals, such as small carnivores, should also not be overlooked.”
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