Here’s what we know about Omicron XE – the new Covid variant found in the UK

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A new Covid-19 variant has been identified in the UK, combining two different Omicron strains, and it could be the fastest-spreading Covid variant, according to initial data from UK health officials and the World Health Organization, although experts warn it’s still closed early to determine whether or how strong the variant might pose a threat.

Important facts

The variant, named XE, was first detected in England in mid-January, according to the UK Health Security Agency (UKHSA), and has since been confirmed in more than 600 cases in England, less than 1% of the virus samples analyzed at that time.

As of March 22, 763 samples of XE have been identified in the UK and a very limited number of cases have reportedly been found in China and Thailand.

XE is a recombinant virus – essentially a combination of genetic material from two or more different viruses – containing elements of the original omicron strain BA.1 and the more contagious BA.2 subvariant, also known as the “stealth omicron”.

Early data from the UKHSA and WHO suggests that the XE variant could be around 10% more transmissible than the Omicron subvariant BA.2, which is already the most contagious Covid variant and one of the most contagious diseases in human history .

Susan Hopkins, UKHSA’s senior medical adviser, said more data is needed to confirm whether XE has a “real growth advantage” as it has shown a “variable growth rate” over the time it has been monitored so far Has.

There is also not enough evidence to draw any conclusions about the transmissibility, severity or effectiveness of the vaccine, Hopkins said, adding that the UKHSA will continue to monitor the situation “closely”.

key background

It is normal and to be expected that viruses change over time. Many of these changes are the result of genetic mutations, but some larger changes can occur when a person is infected with more than one type of virus. When this happens, viruses can swap and swap parts of their genetic makeup as they replicate inside our cells, effectively creating a hybrid with elements from both “parents”. Recombinant viruses are “not an uncommon occurrence,” Hopkins said, “especially when multiple variants are in circulation.” A number of Covid recombinants have been identified during the pandemic, she noted, and most “die off relatively quickly,” as with other variants.

What we don’t know

How a new variant will affect Covid treatments. New variants may evade existing vaccines and treatments for Covid-19. For example, Omicron is better able to avoid the protection offered by vaccination and previous infections, and both BA.1 and BA.2 are resistant to most monoclonal antibody treatments. AstraZeneca’s treatment, Evushield, still appears to work against the variants, as do antiviral drugs Paxlovid and Molnupiravir. There is no data yet on whether XE can evade these treatments.

What to look out for

A new named variant. The WHO assigns Greek letter names such as alpha, delta, and omicron to variants of special interest or interest. This is based on significant behavioral differences between variants, not just genetic differences. Two omicron subvariants – BA.1 and BA.2 – are still classified as omicron, although genetically they are about as different as earlier variants Alpha, Beta and Gamma from each other. The WHO said it will classify XE under the Omicron umbrella until “significant differences in transmission and disease characteristics, including severity, can be reported”. These differences have not previously been reported.


The UKHSA said it was also monitoring two other Covid recombinants: XD and XF. Both variants are a genetic mix of delta and omicron BA.1. Only 38 cases of XF and no cases of XD have been identified in the UK since mid-February. Just 49 cases of XD have been reported in global databases, the UKHSA said. Most of these were found in France.

Surprising fact

Coronaviruses are known to recombine with other virus types, including influenza and rotaviruses. While it may be unlikely given the rarity of successful recombinants, it is plausible that a variant could arise from a combination of SARS-CoV-2, the virus behind Covid, and another virus. Such a recombinant could have new and unexpected properties

Further reading

The raging evolutionary war between humans and Covid-19 (Wired)

Evolutionary landscapes predict what’s next for the COVID virus (Quanta)

Coronaviruses can recombine with cellular and heterologous viral genes to generate unexpected variants (Forbes)

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