As of April 5, 2022, 1,125 cases of XE, a new co-combinant subvariant, have been identified in the UK, up from 637 on March 25.
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Japan has reported its first case of omicron XE, a new strain of Covid-19 first detected in the UK — just as the British cases of the subvariant increase.
The XE variant was found in a woman in her 30s who arrived at Narita International Airport from the United States on March 26. The woman, whose nationality was not immediately disclosed, was asymptomatic, Japan’s health ministry said on Monday.
It comes as cases of the new strain have almost doubled in Britain, according to the latest statistics from the UK Health Security Agency.
As of April 5, 1,125 cases of XE had been identified in the UK, up from 637 on March 25. The first confirmed case has a specimen date of January 19 of this year, suggesting that it could have been in circulation in the population for several months.
XE is what is known as “recombinant,” a type of variant that can occur when an individual is infected with two or more variants at the same time, resulting in a mixing of their genetic material within a patient’s body.
In XE’s case, it contains a mixture of the previously highly infectious BA.1 omicron strain, which emerged in late 2021, and the newer “stealth” BA.2 variant, currently the dominant variant in the UK.
Such recombinants are not uncommon, having occurred several times during the course of the coronavirus pandemic. However, health experts say it is too early to draw any conclusions about the new subvariant’s severity or ability to evade vaccines.
“We continue to monitor cases of the recombinant XE variant in the UK, which currently account for a very small proportion of cases,” Meera Chand, director of clinical and emerging infections at UKHSA, said in a statement.
On Sunday, the UK reported 41,469 new covid cases, with a seven-day average of 59,578 cases. As such, XE is likely to account for only a small percentage of total Covid cases currently.
Early estimates suggest that XE may be more transmissible than previous strains, as it has so far shown a slightly higher growth rate than its predecessor.
UKHSA data shows that XE has a growth rate of 9.8% above BA.2, while the World Health Organization has so far pegged that figure at 10%.
However, experts say they expect it to decrease in severity even as it spreads more easily. XE has so far not been declared a variant of concern.
“XE appears to be moving in the same direction as BA.2, with higher transmissibility than BA.1 but less severe,” Jennifer Horney, a professor of epidemiology at the University of Delaware, told CNBC.
“It’s the devil we know, so to speak. [It is] essentially a reshuffling of the same deck of cards,” added Mark Cameron, an associate professor at Case Western Reserve University School of Medicine.
XE contains spike and structural proteins from the same family of viruses, ie omicron, which means that it should, at least theoretically, behave as omicron has done before. Therefore, existing vaccines and immunity should provide some level of protection against infection.
“It is quite likely that recombinants containing the spike and structural proteins of a single virus (such as XE or XF) act similarly to [their] parental virus,” wrote Tom Peacock, a virologist in the Department of Infectious Diseases at Imperial College London, in a tweet thread at the middle of March. XF refers to other recombinant previously detected in the UK in February.
However, other recombinants containing spike and structural proteins from different virus families continue to emerge. That includes the XD subvariant, recently discovered in Germany, the Netherlands and Denmark, which contains delta structural proteins and omicron spike proteins and which Peacock described as “a little more concerning.”
As such, all new appearances should be closely monitored, especially in their early phases, to ensure they don’t escalate into something more serious.
“The virus is still capable of evolving, recombining and developing a new branch of its family tree,” Cameron said.
“The key takeaway is that for each of these variants and subvariants, the risk of hospitalization and death appears to be, on average, lower where vaccination rates are higher, indicating that vaccination, including a third dose, should be effective in reducing the risk of severe disease. disease,” added Stephanie Silvera, a professor of public health at Montclair State University.