It’s a fight in which the rules and the adversaries change all the time: as the pandemic accelerates, new variants appear and challenge scientific research.
How many variants?
Like any RNA virus, Sars-Cov-2 has already mutated thousands of times: this is its natural evolution. Each time the virus replicates, copy “errors” change it. And again: this virus is known to be rather stable.
Most mutations have no concrete consequences for humans.
But several variants show a substantial change in their characteristics: more contagious, more pathogenic, more resistant, etc.
These mutations work on the principle of natural selection: when a variant acquires a “selective advantage”, it asserts itself fairly quickly, being “stronger” than its predecessor. Very concretely, the British variant being more contagious, it is logical that it replaces the “classic” virus, since it spreads faster.
Conversely, if a less contagious variant emerged – it has probably already happened – it is likely that we do not even realize it: it would quickly disappear under the pressure of other “versions” of the virus.
To date, three significant variants have been identified with certainty, known as “British”, “South African” and “Brazilian” – this is not necessarily their origin but the place of their identification and / or their “installation. “.
The first appeared in Kent (south-eastern England), probably in the fall, and was reported to WHO on December 14 as more transmissible.
It is now predominant in Great Britain. It is now circulating in at least 57 countries … where it will replace in a few weeks the previous strains, less well “armed”.
> Click on the map to enlarge it
The second would have appeared in August in South Africa, where it has since become the majority. It was reported to the WHO on December 18.
Still quite rare in France, it was detected there for the first time, in Alsace, by a resident returning from Africa on December 31. Several other cases have since been identified, and this variant has been found in at least 23 countries.
> Click on the map to enlarge it
Finally, are there one, two Brazilian variants? Or more? According to this article in Le Monde, published in the blog “Réalités biomédicales”, there would be at least two : a first identified in the region of Manaus (Amazonas) in December, particularly worrying. And a second, imported to Japan by four travelers returning from Brazil.
But this one, according to Japanese health authorities, would not be the same …
They are numerous, but only a small number really worries: those which affect the famous protein Spike (or spicule, or “protein S”). It is used by the virus to enter our cells … and it is targeted by vaccines to neutralize it.
The N501Y mutation has been identified on all of these new variants. It is, among other things, responsible for their greater transmissibility, by allowing the virus to penetrate more easily into human cells.
The K417T / N and, above all, E484K mutations have also been identified on the South African and Brazilian variants.
It is almost certain that the N501Y mutation makes the virus more contagious but, a priori, not more deadly.
But in reality, it would have been better to have a virus twice as deadly than twice as contagious: the first will kill twice as many. The second will rapidly explode the number of cases, and therefore the number of deaths, as Guillaume Rozier, founder of CovidTracker explained to us in this article.
With, in a month, a 30 or 50 multiplication of the number of contaminations … and deaths in the same proportions.
> Update on the British variant in this video
Another concern of the E484K mutation is that it could make the virus less receptive to vaccines, because it would be less easily identified by antibodies.
Clearly, a bit as if it were a new virus. At best, the vaccine would be a little less effective. At worst, it wouldn’t be at all.
The disturbing E484K mutation
The University of Seattle published in early January work on viruses carrying the E484K mutation: for the moment, they confirm that these variants are much less well detected by the antibodies of former covid patients.
Jesse Bloom, head of the Seattle team, is reassuring first: “No one should be worried about a single catastrophic mutation that would suddenly render all immunity and all antibodies unnecessary,” he said. “It will be a process which will take place over a time scale of several years and which will require the accumulation of multiple viral mutations”, he explains.
However, his work on the Brazilian variant identified in Japan shows its worrying proliferation in a region where 76% of the population has natural antibodies (read below).
These few mutations are only a tiny part of the whole and researchers fear new ones … or even a deadly combination of these mutations.
If these changes may seem abstract, their consequences are clearly visible.
The express reconfinement of the United Kingdom, exactly one month after deconfinement, on December 4, no doubt a little hasty, showed it: a health system at the end of its rope, paralyzed by an explosion of contaminations.
Direct consequence: mortality has also soared to record levels, despite emergency health measures taken by Boris Johnson just before and just after Christmas.
In Manaus, Brazil, a massacre is attributed to the E484K mutation. Ephemeral example of “collective immunity”, the city where 76% of the inhabitants had antibodies against Sars-CoV-2 quickly became disillusioned.
It is now plunged into indescribable chaos, its inhabitants queuing for hours to fill their oxygen cylinders paid for at a high price and try to keep their loved ones alive, at home.
In the hospital of this metropolis of 2 million inhabitants, the lack of oxygen has caused the death of dozens of patients and the nursing staff are overwhelmed.
In the cemetery, the “square” reserved for the dead of covid-19 continues to expand …
In question: a priori, this famous E484K mutation, making the virus less sensitive to the immune response.
With a first documented case of reinfection this fall: treated in June for a proven covid, a 37-year-old woman was reinfected in October by a more serious form, by a variant carrying this mutation. A serious clue in favor of this hypothesis … which would explain the hecatomb that Manaus has undergone in recent weeks.
Since then, a laboratory experiment has confirmed the theory: when confronted with the plasma of a cured patient – and therefore with his antibodies – a coronavirus has been pushed to mutate. Verdict: after three months, a variant with the E484K mutation appeared.
So many concordant clues which are not (yet) scientifically proven, but are extremely worrying.
That’s the whole problem: like when the disease started to spread in early 2020, we still have more questions than definite answers.
Start with: will the vaccines remain effective? Impossible to say to this day. The only certainty is that they “target” several “parts” of the famous Spike protein, and not the only ones affected by mutations.
But the multiplication of these could, in the long term, reduce the vaccine effectiveness.
Laboratories assure for the moment that they will be able to “adapt” their vaccines fairly quickly if necessary. That it would be necessary, once again, to produce and administer massively.
Especially if we do not manage to vaccinate the population quickly enough, or if we space the first and second injections too much. Precisely favorable circumstances to circulate the virus.
Space out vaccine doses? As we explained in this article, the virologist Paul Bieniasz believes that he “would not go about it otherwise if he wanted to cause the appearance of vaccine-resistant variants”.
In addition to the mask, hydroalcoholic gel or other barrier gestures, maintaining a physical distance between each person is more essential than ever, at a time when the virus has never circulated so much on the planet. And in even more dangerous forms than before.
A major problem would remain: that of the inevitable appearance of other new variants, of which the “strongest” versions would take precedence over the others. It is only a matter of time, as the Director General of the World Health Organization reminds us:
The more Covid-19 spreads, the more likely it is to evolve. Note that the transmissibility of certain variants of the virus seems to increase
Tedros Ghebreyesus, Director-General of WHO
Source: A la Une – Le Progrès | Le Progrès by www.leprogres.fr.
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