The variant AY.4.2 represents almost 10% of the cases sequenced in Great Britain: it could be 10% -15% more transmissible, but it cannot be the only cause of the high number of Covid cases in the UK
Under the lens, in Great Britain – where in recent days there has been a growth of new coronavirus infections and deaths caused by Covid: and here we try to explain the reason for this increase – there is a Delta sub-variant which already represents almost 10% of the cases sequenced in the country and would be on the rise: it is called AY.4.2.
The transmission capacity
It is not the only sub-type of Delta widespread in the UK, where it has been present for months, but scientists are monitoring its transmission capacity: two experts – Jeffrey Barrett, director of Covid-19 Genomics Initiative at the Wellcome Sanger Institute in Cambridge, and Francois Balloux, director ofUniversity College London Genetics Institute – stated that AY.4.2 appears to be 10 to 15% more transmissible than Delta, but the data is far too uncertain. The prevalence of AY.4.2 is increasing rapidly, but it has taken several months to reach nearly 10% of new infections and its growth rate is very variable in the different regions. While it may have an advantage, it is not spreading with the kind of ‘explosive’ speed seen for the Delta strain upon its entry into the UK. Furthermore, it is not yet widespread outside the United Kingdom: in the United States the prevalence has increased, but has subsequently decreased or remained at constant levels, and this could show that the greater prevalence in some areas is the result of multiple random factors concomitants.
The rise of cases in Britain
Scientists, in fact, seem to deny that AY.4.2 is directly responsible for the very high levels of Covid cases, hospitalizations and deaths in the UK, far above those recorded elsewhere in Western Europe. The reasons that explain the resurgence of the virus in the English-speaking country are many: the abandonment of all restrictions (including the use of masks indoors and distancing), the immunity conferred by the vaccine which is decreasing after six months and the poor vaccination coverage of the population 12-17 years (we talked about it in full HERE
), but also a certain indifference of the population that no longer feels Covid as an important issue.
It is not a Delta “plus”
But what are the characteristics of AY.4.2 known so far? First the name: AY.4, AY.9, AY.4.2, are all underlines of B.1.617.2, the Delta variant. The use of the term “Delta plus” is incorrect: has caused confusion in the past and should be avoided, also because it has already been applied to previous descendants of Delta with mutations other than those of AY.4.2.
AY.4.2 is one of the 45 Delta descendants which have been registered all over the world. Brings two mutations characteristics in the spike protein with which the virus infects human cells, called Y145H and A222V. Both mutations have already been recorded individually in previous coronavirus lines, although not in VOCs, ‘variants of concern’, so we don’t know if they have characteristics that make the virus more infectious, more virulent, or more insidious for vaccines. “A222V has been seen in other Delta lineages,” said Ravi Gupta, Professor of Clinical Microbiology at Cambridge University: “It does not have a very large effect on the virus, but it remains difficult to predict the effect of individual mutations on viral behavior” .
The reasons for concern
Scientists speculate that the only path to the evolution of SARS-CoV-2 is, however, through the single mutations of the Delta, just like the one that gave rise to AY.4.2. In fact, where it has established itself, Delta has canceled even the most worrying variants with respect to the ability to “pierce” vaccines. The main feature of the variant (which is now predominant around the world) is not to evade vaccine protection, but to be more transmissible. Rather, the major concern is related to the fact that in much of the world the infections remain uncontrolled and this gives the virus more chances of evolution as it spreads through the human population. SARS-CoV-2 is a virus capable of infect many different mammals. He is known for doing the “Leap of species” from humans to minks and back to humans. Zoo keepers around the world treat coronavirus infections among lions, tigers, gorillas and other animals in captivity. Mutation is a numbers game. Whenever the virus replicates, it mutates and the Delta sub-lineages suggest that evolutionary paths towards greater transmissibility are still open.
Mutation is a numbers game
THE widespread vaccines are used to curb the number of mutations and the indispensable sequencing work is used to monitor the evolution of the virus. In the world, however, there are still millions of Delta cases that run in unvaccinated populations and that are not detected by genomic sequencing.
October 20, 2021 (change October 20, 2021 | 13:32)
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