It seems that every few weeks we hear about a new version of Covid and it is difficult to understand how concerned we should be.
A “recombinant” variant called “Omicron XE” has emerged, resulting from two strains of omicron that fuse together into one host and then continue to infect others.
So what do we know about this new hybrid and should we worry?
A little about Omicron and its variants
Omicron is a variant of the SARS-CoV-2 virus, which was first detected in Botswana on 11 November 2021 and identified by the WHO as a dangerous variant on 26 November. From that moment on, it was transferred around the world and replaced Delta to become the dominant option.
Since then, Omicron has continued to evolve to have many different lines or genetically related subvariants. This includes the original Omicron BA.1 (B.1.1.529), as well as BA.2 and BA.3.
BA.2 is more contagious than BA.1 and has now taken over or overtaken BA.1 to become the new dominant form of SARS-CoV-2 virus worldwide, with the WHO officially announcing that this will be the case. March 22, 2022.
The differences we saw in Omicron compared to previous variants are explained by the relatively large number of mutations it has acquired, such as 60 mutations not found in the original virus originating from Wuhan, China.
Among these mutations are 32 genetic changes in the thorn protein. Thorn protein is the part of the virus that it uses to attach to human cells, as well as the purpose of the immune response against the virus, both from vaccines and from previous infections.
BA.2 shares many of the same mutations as the original version of Omicron, but also has 28 unique genetic changes of its own. Four of these genetic changes are in the thorn protein, which explains why some of its characteristics are different from the original version of Omicron (BA.1), including the fact that it appears to be approximately 30 to 50% more infectious than BA.1.
What is “recombinant”?
Just as we have seen the emergence of new variants, followed by the evolution of subvariants or different lines, the SARS-CoV-2 virus has continued to change in other ways. Recently, we have seen not only spontaneous changes in the genetic code that have explained the changes described above, but also the so-called recombinants.
Recombinant is where related viruses exchange genetic material to produce offspring with genetic material from both parent viruses. This can occur when viruses from two different strains (either variants or subvariants) co-infect the same cell.
The genetic material of the viruses can be mixed and packaged together to form a new recombinant virus, with properties of one or both parent viruses. Therefore, the properties of the recombinant virus depend on which parts of the genetic material from the parent viruses are included in the new version – just as you can have your mother’s nose and father’s knees.
When Delta and Omicron recombine, the resulting progeny are called “Deltacron” (although more officially they are called XD and XF). This type of recombinant was first identified in France in mid-February and appears to have a genetic sequence almost the same as Delta, but with aspects of the Omicron BA.1 thorn protein.
So what is XE and where does it spread?
XE is a recombination of BA.1 and BA.2. There are many other BA.1 and BA.2 recombinants, including XQ in the United Kingdom, XG in Denmark, XJ in Finland and XK in Belgium.
Although XE still includes a small proportion of total sequenced cases, it showed evidence of transmission in the community, at least in England, where it was first discovered in mid-January. Just over 1,100 cases are currently registered.
It has also been identified in India, China and Thailand. Initially, the growth rate for XE did not seem to differ significantly from BA.2, but more recent data from the United Kingdom suggest that it has a growth rate of about 10 to 20% above that of BA.2.
This data remains preliminary and is based on small numbers, so it may change as we receive more information. If true, then this means that XE will probably be slightly more contagious than BA.2, which was slightly more contagious than BA.1, which was more contagious than Delta.
Do we have to worry?
Our immune response, which helps protect against Covid-19, is generated by vaccination or a previous infection and focuses primarily on thorn protein. Given that XE basically has the same spike protein as BA.2, it does not appear that our protection against XE will be significantly reduced.
While this is something that public health agencies and expert groups certainly need to monitor, and they are, it is not really unexpected, given the number of cases we continue to see around the world. So this should not be a cause for further concern to the general public.
The best way to delay the emergence of new variants, as well as recombinants, remains to have so many people in the world protected by vaccination to reduce the group of sensitive hosts in which these events can occur.
Paul Griffin, Associate Professor, Infectious Diseases and Microbiology, University of Queensland
This article was republished by The Conversation under a Creative Commons license. Read the original article.
Read also: How effective is the omicron-specific vaccine – everything you need to know about variant vaccines
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