We first heard about the omicron strain at the end of November 2021, when the first sequences of the SARS-CoV-2 coronavirus genome obtained by sequencing samples from patients from South Africa and Botswana were uploaded to the GISAID international database. They attracted the attention of scientists with a very large number of mutations, especially in the spike protein gene, and even then they suspected that such a variant of the virus might have some special properties.

We have previously detected at least a fraction of omicron mutations in other significant strains - the same "alpha", "beta" or "delta", but we have never seen so many of them at once in one genome, and from this unpleasant predictions followed regarding a possible increased transmissibility of the virus, as well as the ability to bypass the immune defense. Indeed, the number of downloaded omicron genome sequences in the international database grew very rapidly, as did the number of cases in South Africa, and soon after that it began to be found in other countries, almost replacing the delta variant in most regions of the planet. Under the first blow were those countries that had established active air links with the countries of South Africa - for example, Great Britain. However, they also have the first began to decline in the incidence. The latter made it possible for other countries to predict the epidemiological situation in their territories. But one way or another, now "omicron" is ubiquitous, although it is not a fact that it will completely displace the "delta" due to weakened cross-immunity.

The new strain itself actually turned out to be much more contagious than all previous strains, and, moreover, it was able to partially bypass the immune defenses of both those who had previously been ill and those vaccinated, especially those who were ill or vaccinated a long time ago./i

However, it is still worth making a reservation here. The often-cited mild course of the disease when infected with "omicron" is not necessarily only a property of the newest strain. In fact, in most countries of the world, the vast majority of the population has already been immunized in one way or another. Somewhere this was achieved with the help of an active vaccination program, somewhere, as, for example, in South Africa, the percentage of those who were ill was very high (according to unofficial data, up to 80-90% of the country's population were ill), but in general, many have already been ill and have been vaccinated, and these now have the strongest protection against the virus. If "omicron" had appeared in 2020, then the consequences could be similar to footage from a horror movie. Therefore, the true lethality of this strain simply no longer manifests itself - the environment has changed.

It is also worth noting that the increase in the number of children's hospitalizations around the world now may be due to the fact that this group was mostly not vaccinated and, in addition, the children were partially immune to other strains, at least the virus was much more complicated than them. infect. Therefore, it was this group that remained one of the most defenseless against the "omicron". In general, a vivid example of the benefits of vaccination.

At the same time, let me remind you that before the “omicron”, the “delta” raged with might and main, which caused rises in morbidity and deaths all over the world. In India, in May 2021, up to 400 thousand new patients were officially detected daily, and the situation in hospitals was simply catastrophic. Now in India, on the “omicron”, although the numbers for sick and fatal outcomes are high, they are still significantly lower than in the “delta”, which also shows an increase in the proportion of the immune layer among the population and a certain transition of the pandemic to the status of endemic. It's just that somewhere this was achieved with the help of vaccination, and somewhere - at a high cost to the health and lives of people. And often, at least in developed countries that have their own vaccines, it was the population that chose their own path to gain protection against the virus.

As for the various sub-variants, the same "delta" was divided into a large number of sub-lines, which, however, did not differ much from each other in properties, and rarely one began to outperform the others. But at the same time, there was a stratification of many delta lines into individual countries. And some, including Russia, had their own dominant sub-lines. It was also believed by many that the “delta” would become the final branch of the evolution of the coronavirus and then we would see only some minor improvements in the pathogen. However, the virus deceived us again, appearing in a new guise of "omicron".The now dominant strain of this strain, known as BA.1, is responsible for the overwhelming number of confirmed new cases of coronavirus worldwide. As of January 31, 2022, BA.1 accounted for 96.4% of the sequences uploaded to GISAID, according to the WHO. However, another sub-variant known as BA.2, which differs from BA.1 by a couple of dozen mutations, has already begun to supplant it in some regions. At the same time, some experts believe, and justifiably, that BA.2 is not a descendant of BA.1, but rather some independent branch that could, as they say, come out of the same patient in South Africa, which gave birth to "omicron", although the question of the origin of the latter remains open. Therefore, BA.2 is often referred to not as a daughter, but as a “sister” subline of BA.1. The distribution of BA.2 is now closely monitored in many countries, including Denmark, India and Nepal, where this line has become dominant, and therefore we know about some of the unique properties of the subline.

BA.2 has also been called "invisible" because it lacks a genetic deletion of two amino acids in the spike protein, the part of the virus that helps it enter human cells. Actually, this mutation was used by many foreign PCR tests in order to detect the Omicron strain, distinguishing it from the Delta. And then it turned out that, as it were, “omicron”, but there is no deletion, and therefore the tests missed. It is worth saying that sequencing of the virus genome is guaranteed to detect all changes in the nucleotide sequence of the pathogen, and in this case, errors are practically excluded. In addition, so far no difference has been found in the severity of the course of the disease caused by the two omicron sub-variants. And a separate open question is whether it is possible to get infected with BA.2 after BA.1, and vice versa. So far, no such cases have been documented.

However, BA.2's increased transmissibility means it could become the dominant strain worldwide, but it could also disappear if it is displaced by another variant or faced with effective countermeasures.

For this reason, work on the study of the genomes of the new coronavirus has been significantly intensified at the moment, and the number of downloaded genomic sequences in the VGARus database is rapidly growing, now amounting to almost 90,000 records, of which a third will be in 2022. Now there are more than 14 thousand sequences of "omicron" in the database, of which BA.2 is about 500. Cases of infection with the third line of "omicron" BA.3, which also has its own differences and is not widely used in the world, have noted in the Russian Federation.

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