Covid-19: Did the variants really arrive without warning?

Forum Science Covid-19: Did the variants really arrive without warning?

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    Covid-19: Did the variants really arrive without warning?

    Variants of SARS-CoV-2, the virus responsible for COVID-19, are spreading across the world and causing concern. However, these mutations are a normal and predictable phenomenon. Explanation.

    The origin of the question

    On February 3, 2021, the program director and tracing the at the British Ministry of has been taken to task by scientists for claiming that “no one could have predicted” that the COVID virus could cause more contagious variants.

    Without going as far as the British official, several people have suggested in recent weeks that the emergence of the current variants could not have been predicted.

    Why are there mutations?

    All viruses mutate and evolve with the . SARS-CoV-2 is no exception, with about one mutation every ten . These mutations are copying errors that occur randomly when the virus infects cells of a host and replicates.

    You should know that viruses cannot reproduce by themselves (unlike bacteria). They carry their “manual of”that they impose on the cells of the living being that they infect. It is therefore these cells of the” host “which will make new copies of the viruses.

    And it is in making these copies that cells sometimes make mistakes, usually in the form of a single false “letter” among the tens of thousands that make up the virus. These typos are called mutations. The virus carrying one or more new mutations is a “variant” of the original virus.

    More contagious variants, sooner or later

    It was therefore inevitable that variants of SARS-CoV-2 would appear. as it was inevitable that sooner or later one of these variants, or more of them, would be more contagious than the others. It is in the of biological evolution: in the same way as in animals, for millions of years, those which were better adapted to their changing have survived, a virus must also adapt in order to survive. And in this case, the changing environment is us: our , our confinements, our drugs. The more people who have developed antibodies to this virus, or the more people who avoid gatherings, the less likely the virus is to reproduce. Unless one variant suddenly turns out to be tougher than the others.

    However, we can partly agree with those who claim that we could not predict the current more contagious variants: the nuance is that we could not predict when such mutations would occur.

    The majority of changes have in fact no impact on the development of the , because they do not modify the capabilities of the virus. These mutations are said to be silent. And in the case of SARS-CoV-2, they will generally be corrected in the following generations of the virus thanks to the “corrector” that it has. Other types of mutations are considered to be defects that will harm the virus. For example, mutations will alter the building blocks of proteins encoded in DNA or RNA, altering the final shape of the and prevents it from functioning normally or being transmitted.

    At the, some mutations will give an “advantage” to the virus: allow it to replicate and spread more quickly, to attack the body more severely or to infect new organs. In the virus , the mutation of a who the production of a protein present at the of the virus can allow it to attach more easily to the cells to be infected.

    In the end, the ensures that the mutations that are most beneficial to the virus are more likely to settle permanently in its to form a new variant.

    Another problem is that the rate at which mutations occur is difficult to establish and depends on the virus. Even once we know it (about one mutation per 10 days in the case of this coronavirus) the rate at which “dangerous” mutations occur is impossible to determine. But the fact remains that, in the case of SARS-CoV-2, several studies carried out in 2020 had identified mutations capable of making it more contagious.

    Since the first complete decoding of the SARS-CoV-2 genome, in January 2020, more than 80,000 different mutations have been identified and at least three variants have been identified. This information can be found on Nextstrain, a public which makes it possible to follow the progression of the variants of this coronavirus in the .

    Verdict

    Viruses are constantly mutating. And as long as there is a high in people who will not be immune, the virus will have a high number of chances of reproducing and causing a mutation – which could be good for it and bad for us.

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Forum Science Covid-19: Did the variants really arrive without warning?