• May 28, 2023

Omicron 5 triggers the infections, the identikit of the variant

After weeks of almost universal decline, Covid cases start to increase in different parts of the world: South Africa started, then the USA, now Europe too, with Portugal inaugurating the recovery and the other countries (Germany in primis) to follow, including Italy where the weekly incidence starts to rise after several days of increases compared to the previous 7 days. Covid raises its head, driven by a new sub-variant of Omicron: version number 5, precisely named BA.5, monitored by the world health authorities since mid-May, together with its “cousin” BA.4.

The most contagious version

In the evolutionary race of the virus, it is so far the most contagious version, by far the most infectious of the original virus that came out of Wuhan, which has now become the most contagious virus ever after a “rivalry” that lasted a few months with measles. In the US, BA.5 represents 6-7% of the total number of infections based on the latest data at the end of May: just a month earlier it was 0.2%. Even in Italy, where the decline as mentioned has slowed down and seems to be about to become an increase, the last survey a month ago spoke of an Omicron 5 just at 0.4%, but it is these days the announcement by Minister Speranza di another rapid investigation to quantify the presence of the new sub-variant, which will certainly be significantly increased.

As with all the variants that emerged in these two years, if there are still no solid certainties about its lesser or greater severity (even if some mutations are similar to those of the Delta variant, the more aggressive), it is already evident, in short, the its greater transmissibility, also due to at least two mutations that allow it to bind to human cells more effectively. By making the antibody protection related to healing or the vaccine, including booster, less solid.

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The reinfections

It is no coincidence that in various Regions there is already an increase in reinfections, with Lazio reaching 10%. According to a US study, BA.5 is more than four times more able to dribble our defenses than BA.2, the Omicron sub-variant that contributed to the flood of cases last winter. This is mainly due to the L452R mutation, also common to BA.4, which significantly changes the structure of the spike protein that the virus uses to attach our cells, and against which the available vaccines act, albeit in different ways. Furthermore, according to the first analyzes, the new sub-variant would be syncytium, that is, it causes the infected lung cells to merge with the adjacent healthy ones.

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What will happen in the fall?

Now it is a question of understanding whether BA.5 will limit itself to the summer “ondina”, which also took place last year (but a month later), or will it be the protagonist of the foreseeable new autumn wave, as the virologist warns. Fabrizio Pregliasco: “The most worrying aspect – confirms the expert – certainly concerns the ability of the variant to escape the immune response elicited by the vaccine and that deriving from vaccination. For now Omicron 5 does not constitute a danger in Italy, but suggests an autumn perspective with a possible rise. It had been foreseen, but we hope that the ascent of the curves, which was expected near the winter months, will not be anticipated “.

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