Covid, the most contagious BA.5 sub-variant of the other Omicrons

The BA.5 subvariant is more transmissible than the other Omicron subvariants due to at least two mutations which allow it to bind to human cells more effectively. The data are online on the BiorXiv platform, which hosts studies not yet reviewed by the scientific community, and are the result of research conducted in Japan and coordinated by Izumi Kimur, of the University of Tokyo. “This would explain the increase in cases in Portugal – virologist Francesco Broccolo, from the Bicocca University of Milan told ANSA – and indicates that it is really premature to say that the SarsCoV2 virus is weakening”.

The sub-variant BA.5 it arrived almost at the same time as the BA.4 and, according to the most recent data from the British Agency for Health Security (UKHSA), relating to 8 May last, at the time in Portugal it represented the 18.47% of the SarsCoV2 virus in circulation, against the decidedly lower percentages of other European countries, such as Germany and Great Britain (in both equal to 1.28%) and then France (0.88) and Denmark (0.41%). Italian data from the Istituto Superiore di Sanità indicated that on May 3 the BA.5 sub-variant constituted the BA.5 0.4% of the SarsCoV2 virus circulating in the country. By 20 May the circulation of the BA.5 in Portugal had already increased to 37%.

I am at least threenotes Broccolo, i reasons that allow you to put in relation the presence of BA.5 With the’increase in cases in Portugal. The firsthe notes, consists in the fact that “the subvariants BA.4 and BA.5 are very similar to each other because they both have the L452R mutationwhich alone is capable of to change very much the structure of the Spike proteinwith which the virus attaches to human cells “, he observes.” It is not a new mutation – he continues – because the virus had already selected it in the variants Delta And Lambda“and his presence” would increase the reproduction numberthat is, it would render the two subvariants more contagious compared to other sub-variants of Omicron, such as BA.1 and BA.2 “.

The second elementcontinues the virologist, is provided by the data according to which “the two sub-variants they would escape more to antibodies, both to those generated by the vaccine and to those generated by infections caused by BA.1, BA.2 and BA.2.12.1 “.

The third element it concerns the fact that, like the Delta variant, the BA.5 is also syncytium, that is, the virus-infected lung cells fuse with adjacent healthy, uninfected ones. “This characteristic – he notes – has been demonstrated in vitro on cell cultures but we know that there is a correlation between the fusogenic power of a variant observed in vitro and its degree of pathogenicity in vivo, as also demonstrated by its greater virulence in experiments. conducted on animals “.

In light of these elements, according to Broccolo “doubts arise on what has been said so far, regarding the fact that the virus evolves towards an attenuated pathogenicity”. In the past, he continues, “the arrival of the Delta variant showed that it was more pathogenic than the ancestral virus, then came Omicron BA.1, which had a lower pathogenicity than Delta, and now we are seeing that BA. 4 and BS.5 are more pathogenic than BA.2 and have recovered two mutations of the Delta: in the face of these observations – he adds – we must say that the SarsCoV2 virus does not necessarily evolve to become an attenuated virus and we cannot predict when this it will happen”.


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