The more contagious omicron subvariant BA.2 has become the dominant COVID-19 strain in the United States, but international health experts are placing increased focus on a new hybrid variant that may be even more contagious.
The XE variant is recombinant, meaning it consists of genetic material from two other strains, in this case BA.1, the original strain of Omicron, and BA.2, known as “Stealth-Omicron”.
According to an epidemiological update released by the World Health Organization on March 29, estimates show that XE is 10% more transmissible than BA.2, but the results require further confirmation.
The variant was first detected in the UK in mid-January, and 600 cases have since been reported in the country.
The UK Health Safety Authority has said it monitors XE along with two other recombinants, XD and XF, consisting of strains Delta and BA.1.
Health officials in the UK said in late March there was “insufficient evidence to draw any conclusions about growth benefits or other characteristics of this variant” but responded to initial reports of its infectivity.
“This particular recombinant XE has shown variable growth rate and we cannot yet confirm if it has any real growth benefit,” said Susan Hopkins, Chief Medical Advisor for UKHSA.
However, recombinant variants themselves are nothing out of the ordinary, according to health officials.
“Recombinant variants are not an uncommon occurrence, particularly when multiple variants are in circulation and several have been identified over the course of the pandemic to date,” Hopkins said. “As with other types of variants, most die off relatively quickly.”
The WHO said it will “continue to closely monitor and assess the public health risk associated with recombinant variants” and “provide updates as more evidence becomes available”.