Will we be able to sign an armistice with SARS-CoV-2? Or will the arrival of new variants ruin this hope? While in Cyprus combinations between Delta and Omicron appear to have been detected, experts are showing cautious optimism. One thing is certain: in the evolutionary race which has started between the virus and its human host, the competition is proving fierce. Its driving force: adaptation, as always. Because the battlefield is so changeable, both enemies must continually adjust their weapons. On the one hand, the virus is constantly mutating to adapt to the development of our immune defenses and to changes in our behavior. On the other hand, our immune system constantly launches counter-offensives, in response to virus attacks or vaccines received.
“There is a huge amount of surprise in the appearance of new variants. None of the five variants of SARS-CoV-2 of concern were expected ”, admits Etienne Simon-Lorière, virologist at the Institut Pasteur. Three types of worrying variants can appear: mutants that are more transmissible, more virulent or that escape our immune defenses.
If, for humanity, the bar is higher and higher to hope to achieve collective immunity, so is the power of transmission of new variants. But this evolutionary race is not endless. “For the virus, the space of mutations to be explored is relatively constrained, in particular in the region of the Spike protein, which allows the virus to open the locks of human cells”, explains Etienne Decroly, virologist at CNRS (Aix-Marseille University).
Furthermore, “The more time passes, the longer the time to the appearance of more contagious variants”, because the level of requirement increases, estimates Mircea Sofonea, epidemiologist at the University of Montpellier. This is also true for more virulent variants. Such variants may appear, but more and more rarely. In contrast, “The idea that more contagious variants are necessarily less virulent is a fable, he believes. There is no counter-selection between these two characters. “
The H1N1 flu precedent
Some experts are confident. “Omicron is so conqueror that I do not see how another, even more contagious or more evil could emerge and take the top”, estimates Bruno Canard, virologist at CNRS (Aix-Marseille University).
An optimism qualified by other experts. “There is still a risk of the emergence of a more virulent variant”, considers Etienne Decroly. In particular, he points out, the variants circulating today do not carry mutations that boost the affinity of the key virus for the lock of human cells. If so, their virulence could increase.
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