Just when we were beginning to get familiar with the Greek alphabet, thanks to WHO’s revised labelling of variants, we now have a new nomenclature for recombinant variants. They are the X series. Unlike the X-Men of movies, who are a band of popular superheroes, the bunch of X variants is sparking media concerns and the public is sighing ‘not again’. The world is watching to see if these recombinants will be supervillains or fade fast from our screens as minor baddies.
The recombinant variants are hybrid products of different types of the SARS CoV-2 virus. When two of the previously known and actively circulating variants infect the same person (or an animal), an exchange of genetic material can take place between those viruses in the cells of that infected body.
This is like the transfer of passengers from an arriving flight to a departing flight in a busy airport terminal. They join other passengers to fly together on another journey. The departing flight carries a fresh passenger list to a new destination. That list is the genetic code of the recombinant variant.
If bodies of persons with low immunity offer a long time for the viruses to transit and mingle, there will be enough opportunity in those transit airports for exchange of passengers between the flights. On the other hand, if the transit time is very short, the passengers can’t board the new aircraft. Anti-viral drugs may cut short the time that viruses can stay in the body of an infected person and close the window for recombination. A robust immune response from vaccines too helps get rid of the virus fast and denies an opportunity for viral admixture.
The X series made their public entry in UK, where the Health Security Agency announced the detection of three new variants. XD and XF are variants that arise from a combination of the Delta and Omicron B.1 variants. The XE represents a combination of B.1 and B.2 sub-lineages of the Omicron variant.
An XL variant too has been reported from UK. Since then, several other X variants have been reported in different parts of the world: XG and XH (Denmark); XJ (Finland) and XK (Belgium). Several other recombinants too are being reported every day, with names like XM, XL, XQ and XR.
Of these, XE has attracted most attention as it has been reported to have 10% higher infectivity than Omicron BA.2 which is now the dominant variant in most parts of the world. This is despite a high level of vaccinations in UK, from where most of the XE infections have been reported. While XE seems to at the head of the X pack, in terms of infected cases, it is yet to displace BA.2. It has also not displayed higher virulence or a different clinical profile, when compared to BA.2. Upper respiratory symptoms and mild fever appear to the prominent symptoms, with the lungs mostly spared.
Whether the X variants have entered India is presently a matter under investigation. A report of XE sighting from Maharashtra has been refuted by the Union Health Ministry, which said that the experts of INSACOG did not detect the specific genetic pattern of that variant. A later media report came from Gujarat of cases with XE and XM variants.
The Gujarat Biotechnology Research Centre, part of the INSACOG national network of genomic testing laboratories, has confirmed the isolation of XE in a case. While Covid cases have been generally on the decline in the country, recent rise in a few states calls for extensive genomic surveillance to detect new variants, especially the recombinant viruses.
We still need to study the infectivity and immune evasion capabilities of these X forms. As global experience accumulates, we will have better insights into their behaviour. As of now, there does not appear to be any cause for worry that these variants will unleash a major new upsurge in India.
The high level of immunity conferred by Delta and Omicron waves as well as the extensive coverage by the vaccination programme (over 83% of fully vaccinated persons and around 96% having received at least one dose, by early April this year) are likely to protect against severe illness. However, we need to keep our vigil and watch out for any upsurge in cases, while scaling up genomic analysis to study the arrival from abroad, or emergence within our population, of recombinant forms of the virus.
Finally, a public health message that needs to be strongly reiterated relates to the continued need for personal protection through Covid-appropriate behaviour. Irrespective of the form the virus takes, masks can be an effective barrier to transmission. While travel, economic and social activities have resumed, crowded events should be avoided, especially in indoor locations. Good ventilation and airflow should be aimed at, as much as feasible.
The virus is still evolving. Even if its recombinant forms do not have greater virulence, we should try to avoid any infection and not just severe illness. This is because we now know that even asymptomatic infection or mild clinical illness can lead to long term effects in some persons.
Whether it is BA.2 or a recombinant, it is best to protect ourselves with reasonable precautions, while we resume active life. Just as in cricket, we need to maintain a good defence against all types of bowling, while we look to play scoring strokes.
Prof K Srinath Reddy, a cardiologist and epidemiologist, is President, Public Health Foundation of India (PHFI). The views expressed in this article are those of the author and do not represent the stand of this publication.
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