Announced in South Africa and arrived quietly in Europe, Omicron’s BA.5 sub-variant could become a special surveillance: it is its presence that is linked to the sudden increase in Covid-19 cases in Portugal, it is the main suspect also for a increase in cases in Germany and, to close the circle, the first data arrive according to which it has at least two mutations that make it more contagious than its sisters, namely the other sub-variants of Omicron that we have so far learned about, first of all the BA .2. With the exception of BA.4, in which the same mutations have been identified.
This is the general picture that is leading many experts to suspect that BA.4 and BA.5 may be a signal that the SarsCoV2 virus is changing, to the point of causing periodic waves. The debate, to which the journal Nature is dedicating a lot of space on its website, to the point that some experts believe that the sub-variants capable of generating new waves deserve a proper name, as has so far happened for the variants, from Alpha to Delta. “It is really premature to say that the SarsCoV2 virus is weakening,” observes virologist Francesco Broccolo, of the Bicocca University of Milan.
The data from the Ministry of Health indicate for Italy a constant decrease in cases and hospitalizations and a substantially stationary situation of deaths. In 24 hours, the new cases increased from 22,527 to 15,082, identified by means of 123,699 tests, including molecular and rapid antigenic, and a positivity rate of 12.1%. There were 27 deaths, or 20 fewer in one day. As for hospitalizations, they are stable at 218 in intensive care, with 18 admissions per day; in ordinary departments there are 4,411, or 31 less in one day. In Italy, as in the rest of the world, Omicron is the variant of the SarsCoV2 virus that absolutely dominates. As for the two sub-variants BA.4 and BA.5, the data of the Istituto Superiore di Sanità referred to last May 3 indicated that the sequences detected corresponded respectively to 0.47% and 0.41% of the total sequences of the SarsCov2 virus obtained. in Italy.
As for the circulation of BA.5 in Europe, the data of the British Agency for Health Safety (UKHSA) relating to 8 May last indicate that at the time in Portugal it represented 18.47% of the SarsCoV2 virus in circulation (at 20 May had increased to 37%), against the decidedly lower percentages of Germany and Great Britain (in both 1.28%) and then France (0.88) and Denmark (0.41%).
To point out Omicron’s BA.5 as more contagious than the other sub-variants of the same Omicron family are the online data on the BiorXiv platform, which includes studies not yet submitted for review by the scientific community, the result of research conducted in Japan and coordinated by Izumi Kimur, from the University of Tokyo: BA.5, like BA.4, has a mutation that allows it to bind to human cells more effectively, already seen in the Delta and Lambda variants.
According to Broccolo, there are three reasons that could link the presence of the BA.5 sub-variant with the increase in cases in Portugal: the first is the L452R mutation, which alone is able to greatly change the structure of the Spike protein. with which the virus attaches to human cells “. The second element is in the data according to which” the two sub-variants would escape more from antibodies, both those generated by the vaccine and those generated by infections caused by BA.1, BA.2 and BA.2.12.1 “; the third is in the fact, like the Delta variant, BA.5 is syncytogenic, ie the lung cells infected by the virus merge with the adjacent healthy ones.
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