Covid-19: is the pangolin really responsible for the epidemic?

Was the pangolin really the mule that brought us the Covid-19? Does this virus come out of a laboratory? For the moment nothing allows to support the last hypothesis, while more and more works exonerate (a little) the pangolin, which would have been only an intermediary.

SARS-CoV-2 has gradually mutated to enter our cells

To infect and multiply in a cell, viruses need to adapt to the species they are attacking: each lock has its key. More specifically, the chance of mutations means that viruses are regularly born with a key compatible with a different lock from that of the original virus. If it then comes into contact with a species whose cells have the appropriate lock (often surface proteins), it can settle there. This is what happened with SARS-CoV-2, the Covid-19 virus. From mutation to mutation and passing from one species to another, his “key” has come closer and closer to the human “lock”. This lock is the ACE2 protein present on all our cells, which is recognized by a particular version of the viral protein Spike.

The pangolin coronavirus is too far from ours

It is already known that SARS-CoV-2 originates in a species of bat, but not the number or identity of the species that have mediated between them and us. To clarify this mystery, we must compare the genetic code of SARS-CoV-2, contained in its RNA, with that of other versions of itself capable of infecting other species. It is indeed RNA, a long molecule similar to DNA, which mutates regularly, allowing the virus to adapt to the characteristics of a new host. The 2003 SARS coronavirus, for example, was born in a bat, then passed through the civet, formerly called the “muskcat”. The pangolin, sold in the Wuhan market where the epidemic seemed to have started, made a good candidate. But now, the RNA of the Spike protein of the coronavirus that infects the pangolin only corresponds to 89% of that which reaches us humans. A rate much lower than the 99.5% observed between the RNA of the human SARS virus and that of the civet, explain several researchers in the journal Medicine / Sciences.

In search of missing intermediate species

Two hypotheses: either a link in the chain linking the pangolin to humans is missing, or the SARS-CoV-2 of the pangolin is not at the origin of ours, but simply another species in which it is installed from the bat. In the latter case, the Covid-19 would come from another intermediary between the bat and us. In both cases, one or more intermediate species remain to be identified. It could be other pangolins, or another unidentified animal. To unravel this mystery, it will be necessary to sequence the RNA of other coronaviruses circulating in species in contact with humans.

A possible but unlikely laboratory design

However, this research would not make sense if SARS-CoV-2 was designed in the laboratory, as was put forward in 2020. This is theoretically possible, as genetic manipulation techniques now make it possible to modulate living organisms. . However, none of the work done since on the subject has found a reason to consider this hypothesis valid. Among those that made noise, a study pointed to a resemblance between the AIDS virus and that of Covid-19. This publication has since been retracted, because this resemblance only concerned about 20 nucleotides (the “bricks” that make up RNA and DNA) out of 30,000, and could therefore entirely be due to chance.

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