A “recombinant” variant has emerged, called “Omicron XE”, which is the result of two omicron strains merging into a single host and then infecting others. So what do we know about this new hybrid and should we be concerned?
A few words about Omicron and its variants
Omicron is a variant of the SARS-CoV-2 virus that was first discovered in Botswana on November 11, 2021 and was identified as a variant of concern by the WHO on November 26. Since then, it has been broadcast worldwide and replaced the Delta to become the dominant variant. The Omicron has since continued to evolve to have multiple different genealogies or genetically related subspecies. 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 on or surpassed BA.1 to become the new dominant form of the SARS-CoV-2 virus worldwide, with the WHO officially announcing this on March 22 2022. The differences we have seen with Omicron compared to previous variants are explained by the relatively large number of mutations it has acquired, with 60 mutations not found in the original virus 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, both from vaccines and from previous infection. BA.2 shares many of these same mutations with 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 characteristics are different from the original Omicron variant (BA.1), including the fact that it appears to be about 30 to 50% more infectious than BA .1.
What is “recombinant”?
Just as we have seen new variants emerge, followed by the evolution of subtypes or different generations, the SARS-CoV-2 virus has continued to change in other ways. Lately we have seen not only spontaneous changes in the genetic code that are responsible for the changes described above, but also the so-called recombinations. A recombinant is where the related viruses exchange genetic material to create offspring with genetic material from both parent viruses. This can occur when viruses of two different strains (or variants or subtypes) infect the same cell at the same time. The genetic material of the viruses can be mixed and packaged together to create 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 mother viruses enter the new version – just as you can have your mom’s nose and your dad’s knees. When the Delta and Omicron are recombined, the resulting offspring are referred to as the “Deltakron” (although more formally referred to as the XD and XF). This type of recombination was first identified in France in mid-February and appears to have a genetic sequence largely the same as Delta but with aspects of the spike protein from Omicron BA.1.
So what is XE and where does it spread?
XE is a recombination of BA.1 and BA.2. There are many other recombinant BA.1s and BA.2s, including XQ in the UK, XG in Denmark, XJ in Finland and XK in Belgium. While XE still accounts for a small percentage of all sequencing cases, it has shown transmission data to the community, at least within England where it was first detected in mid-January. More than 1,100 cases have now been reported. It has also been found in India, China and Thailand. Initially, the growth rate for XE did not appear to be significantly different 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 is likely to be slightly more contagious than BA.2, which was slightly more contagious than BA.1, which was more contagious than Delta.
Do we need to worry?
Our immune response that helps protect against Covid-19 is created by vaccination or previous infection and mainly targets the spike protein. Since XE has basically 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 bodies and expert groups should definitely monitor, and it is, it is not really something unexpected given the number of cases we continue to see worldwide. Therefore, it should not cause additional concern to the general public. The best way to slow down the emergence of new variants, as well as recombinants, remains to protect those people in the vaccinated world to reduce the number of susceptible hosts to which these events may occur. Paul Griffin, Associate Professor, Infections and Microbiology, University of Queensland This article is republished by The Conversation under a Creative Commons license. Read the original article. Read also: How effective is the micron-specific vaccine – everything you need to know about targeted variant shots