Coronavirus: unknowns and concerns surrounding the new Omicron variant – archyde

Botswana, Hong Kong, South Africa and now Belgium: a new variant of SARS-CoV-2, B.1.1.529, is in circulation. It is already forcing the UK, France and the Netherlands to ban flights from South Africa, the country with the most cases to date.

And this despite the warning from the World Health Organization (WHO), hammered on Friday, November 26 by the voice of Christian Lindmeier, spokesperson: “WHO recommends that countries continue to apply a scientific and risk-based approach (…). At this point, again, the implementation of travel restriction measures is not recommended. “ The body, which nevertheless classified the virus as “Worrying” and baptized it “Omicron”, judge that it will take ” Several weeks ” before knowing the transmissibility and virulence properties of the new variant.

The concern is nevertheless based on several clues, recalling the disastrous arrival of predecessors, such as Alpha or Delta. The first concerns the genetic profile of B.1.1.529, the second, its distribution. But the two aspects still conceal a lot of unknowns, in particular concerning its contagiousness or its escape capacities.

On the genetic side, the springing of Omicron compared to all the other variants is comparable to the emergence of a leaf from a bush, at the end of a branch that would not have made a branch and that no one would have seen him grow. The virus mutated at a rate greater than the average tempo of its congeners, which is about two mutations per month. The “jump” is of the same order as that performed by his predecessor Alpha, who, with a dozen mutations at once, had surprised. A year later, around thirty mutations appear in the main part of the virus, the spicule, through which it clings to its host to infect it; and almost twenty in the other regions of the genome which are used, for example, to manufacture the protective envelope of the virus or the machines necessary for its replication.

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Besides the quantity, it is the list of these mutations that most appeals to specialists, determining the modifications, additions or deletions of “pearls” (amino acids) on the long necklace formed by the proteins of the virus, by changing its main properties: its ability to infect, its propensity to escape antibodies and vaccines and, possibly, its virulence.

Many are well known. In position 484 and 501 of the collar forming the spicule, as in Alpha, Beta or Gamma – but not Delta – pearls are substituted and they are attributed to the effects increasing, respectively, the ability to escape the antibodies induced by the infection or vaccination, and also transmissibility. In 681, we find a modification present in Alpha and Delta, promoting infectivity. On the other hand, the pearl 452, characteristic of Delta, very contagious, has disappeared. A total of nine mutations have already been seen on the variants of concern.

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