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1) A “new” variant? Not so sure
On November 23, South African health authorities notified the World Health Organization (WHO) that they had detected a new variant of the coronavirus. First baptized “B.1.1.529”, then from the Greek letter Omicron, it was declared “worrying” by the WHO November 26 because of about thirty mutations in its S protein (the one that facilitates the infection of our cells by the virus). This is a figure that puts it in a category of its own, since it represents more than double the mutations of the Delta variant, also classified last summer among the “worrying” (in English, variant of concern).
Now, with what biology has learned from evolution since Darwin, it is quite possible that this “Omicron” had, somewhere in the world, “grandparents” with 29 mutations, or 28, or 27, that escaped radar screens. And the first genetic analyzes point in this direction: on the NextStrain platform, which lists the genetic sequences of more than 4000 samples of the coronavirus since January 2020, this Omicron, also called in their jargon “21K” (in red below), shows that it has as its closest “known” relatives, mid-2020 virus.
In other words, samples from South Africa, Botswana and Hong Kong whose genes the researchers analyzed (as of Friday), do indeed reveal to be part of a different family of the virus, but a family that broke away from the others around June 2020. And which has therefore been circulating for a year and a half without samples having been collected for genetic analysis. Clearly, this means that Omicron has probably circulated in one or more countries that do little genetic surveillance – that is, countries other than South Africa, since it has a reputable alert system (Network for Genomic Surveillance in South Africa).
2) Omicron is more transmissible? We do not know
If South Africa has spotted it now, it’s because there has been a sudden explosion in the number of cases in one region of the country, in just a week (from 200 new cases per day to over 2,000 ). This could indicate a very high transmissibility. But it could also be due to the low vaccination rate in the country, only 24%. By comparison, several countries in Europe are currently having surges in the number of cases higher than South Africa, and the unvaccinated are more involved.
3) Could Omicron be vaccine resistant? Unlikely
Each variant that so far has inherited the label of “concern” carried disturbing features. Vaccines have been shown to be as effective, or slightly less effective, but never ineffective. It will be remembered, for example, that the Beta variant, which seemed to have a greater capacity to deceive our immune defenses, was found to have a low transmissibility.
4) Omicron causes more severe cases? We do not know
Reacting, not without impatience, to the storm of speculation, the South African authorities insisted on Friday that the patients observed so far all had “mild” symptoms.
Conventional PCR tests make it possible to quickly identify one of the mutations in the S protein which characterizes this variant, so that with many countries now in a state of alert, new cases will be discovered fairly quickly, which is in turn. quickly give an idea of its level of transmissibility.
Provisional verdict
This virus having reserved its share of surprises for two years, it is normal to play the card of caution, but it is too early to be alarmed. Experts who have spoken on this since Thursday speak of delays of “two to three weeks” before seeing more clearly.
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