By Paul Griffin, University of Queensland Queensland
It seems like every few weeks we hear about a new COVID version, and it’s hard to know how concerned we should be.
A “recombinant” variant has emerged, termed “Omicron Xe”, which is the result of two Omicron strains merging together in a single host and then infecting others.
So what do we know about this new hybrid, and should we need to worry?
A little about Omicron and its types
Omicron is a variant of the SARS-CoV-2 virus that was first discovered in Botswana on 11 November 2021 and designated a variant of concern by WHO on 26 November. Since this time, it has been broadcast worldwide and replaced Delta. major version.
Omicron has since continued to evolve into many different lineages, or genetically related subtypes. It also includes the original Omicron BA.1 (B.1.1.529) and BA.2 and BA.3.
BA.2 is more contagious than BA.1 and has now overtaken BA.1 or has become the new dominant form of the SARS-CoV-2 virus worldwide, the WHO officially announced on 22 March 2022. announced to be. ,
The difference we observed with Omicron relative to the previous variants is explained by the relatively large number of mutations, with 60 mutations not found in the original virus originating from Wuhan, China.
Among these mutations are 32 genetic changes in the spike protein. The spike protein is the part of the virus that it uses to attach to human cells, as well as the target of the immune response against the virus from both vaccines and prior infection.
BA.2 shares many of these mutations as the original Omicron variant, but also has 28 unique genetic mutations of its own. Four of these genetic changes are in the spike protein, which explains why some of its features differ from the original omicron variant (BA.1), including the fact that it appears to be about 30 to 50% more infectious than BA.1. it happens.
What is ‘recombinant’? Just as we have seen new forms followed by the evolution of subvariants or different lineages, the SARS-CoV-2 virus has been changing in other ways as well. In recent times we have seen not only spontaneous changes in the genetic code responsible for the changes described above, but also so-called recombinants.
A recombinant is one where related viruses exchange genetic material so that both parents can produce offspring with genetic material from the virus. It can arise when viruses from two different strains (or variants or subvariants) co-infect the same cell.
The genetic material of the virus can be mixed and packaged together to form a new recombinant virus, which has the properties of either or both of the original viruses. So the properties of a recombinant virus depend on which parts of the genetic material from the original virus make it into the new version – just like you might have your mother’s nose and your father’s knee.
When delta and omicron recombine, the resulting progeny is referred to as a “deltachron” (though more officially these are referred to as xd and xf). This type of recombinant was first identified in France in mid-February and appears to have the genetic sequence mostly identical to that of Delta, but with aspects of the spike protein from Omicron ba.1.
So what is XE and where is it spreading? XE is a recombination of BA.1 and BA.2. There are many other BA.1 and BA.2 recombinants, including XQ in the UK, XG from Denmark, XJ from Finland and XK from Belgium.
While XE still comprises a small proportion of the total number of cases sequenced, it has shown evidence of community transmission, at least within England, where it was first detected in mid-January. Now just over 1,100 cases have been registered.
It has also been identified in India, China and Thailand. Initially the growth rate for XE was not significantly different from that of BA.2, but recent data from the UK suggests that it has a growth rate of about 10 to 20% higher than BA.2.
This data is preliminary and based on small numbers, so it may change as more information becomes available. If this is true, it means that XE is likely to be slightly more infectious than BA.2, which was slightly more contagious than BA.1, which was more infectious than Delta.
Do we need to worry?
Our immune response that helps protect against COVID-19 is triggered by vaccination or previous infection, and it mostly targets the spike protein. Given that XE has basically the same spike protein as BA.2, it does not seem that our protection against XE would be significantly reduced.
While this is something public health agencies and expert groups should certainly be monitoring, and they are, it’s not really something that is unexpected given the number of cases we see around the world. So it should not be a cause of additional concern to the general public.
The best way to slow the emergence of new forms as well as recombinants is to reduce the pool of susceptible hosts in which there are as many people in the world protected by vaccination as possible.
(This article is syndicated by PTI from The Conversation)
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