Covid: the virus changes, but does not become more dangerous

11/26/2020 World



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the SarsCoV2 virus changes, but so far it does not appear to have become more contagious to humans: The good news comes from analysis of viral genomes taken from more than 46,000 Covid patients in 99 countries around the world. The study, coordinated byUniversity College London (Ucl) and published in the journal Nature Communications, documents more than 12,000 mutations, but none appear to have given a particular evolutionary advantage to the coronavirus.

Continues in surveillance It will also be essential in the coming months, experts explain, so that future vaccines can be adapted to any mutant form. In this phase “you have to be vigilant”, say the researchers, because the vaccine could increase the selective pressure on the virus, favoring the appearance of new mutant forms. «We are convinced that we will be able to identify them promptly to adapt the vaccines on time, if necessary ”, reassures the study coordinator, Francois Balloux from Ucl. The immunologist Antonella Viola from the University of Padua also shares the same opinion, underlining that SarsCov2 is “quite stable: variants arise from time to time, but for now the one that has spread to us is always the same. The vaccines under study are effective against the variant in circulation and some in particular, such as Pfizer and Moderna, have this characteristic: if the virus had mutated in a year it would be easy to adapt them.

So far there are 12,706 mutations identified in the SarsCoV2 genome, mostly induced by the action of the human immune system: of these, 398 have been developed several times and independently. The researchers looked at 185 in particular, which appeared at least three times independently during the pandemic. By placing them on the evolutionary tree of the virus, they were able to observe that none of them gave a particular advantage to carriers of the virus.

No mutations increases transmissibilitynot even the famous D614G mutation of the Spike protein. “The virus – says UCL geneticist Lucy van Dorp – may have already reached its maximum adaptation to the human host when we discovered it.” In fact, the virus is estimated to have made the leap from species to humans between October and November 2019, while the first viral genomes studied date from the end of December: “it is possible that at that time – concludes Balloux – the mutations crucial for human transmissibility had already emerged and fixed.”