Home » Health » The variants arrived without warning? False

The variants arrived without warning? False



This article is part of the column of Rumor Detector, click here for other texts.


The origin of the question

On February 3, 2021, the Director of the Virus Testing and Tracing Program at the UK Department of Health was taken to task by scientists for asserting 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 over time. SARS-CoV-2 is no exception, with about one mutation every ten days. 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 “instruction manual” which they impose on the cells of the living being they infect. It is therefore these “host” cells that will make new copies of 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 genetic code of the virus. These typos are called mutations. The virus carrying one or more new mutations is a “variant” of the initial virus.

More contagious variants, sooner or later

It was therefore inevitable that variants of SARS-CoV-2 would appear. Just 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 logic of biological evolution: in the same way as in animals, for millions of years, those which were better adapted to their changing environment have survived, a virus must also adapt to survive. . And in this case, the changing environment is us: our immune system, our lockdowns, 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 mutations have in fact no impact on the development of the disease, because they do not modify the capacities of the virus. These mutations are said silent. And in the case of SARS-CoV-2, they will generally be corrected in subsequent 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, they will modify the building blocks of proteins encoded in DNA or RNA, which alters the final form of the protein and prevents it from functioning normally or from being transmitted.

Conversely, a few mutations will give the virus an “advantage”: allowing it to replicate and spread more quickly, to attack the body more severely or to infect new organs. In the influenza virus, the mutation of a gene that controls the production of a protein present on the surface of the virus can allow it to attach more easily to the cells to be infected.

In the end, natural selection ensures that the most advantageous mutations for the virus are more likely to be permanently fixed in its genome 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, many studies conducted in 2020 had spotted 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 website that tracks the progression of variants of this coronavirus around the world.

Verdict

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

Image: Viktor Bondariev / Dreamstime.com

Leave a Comment

This site uses Akismet to reduce spam. Learn how your comment data is processed.