The most contagious variant of omicron BA.2 has become the predominant COVID-19 strain in the United States, but international health experts are increasingly focusing on a new hybrid variant that may be more contagious.
The XE variant is recombinant, meaning that it consists of genetic material from two other strains, in this case BA.1, the original strain of the omicron, and BA.2, known as the “stealthy omicron”.
According to an epidemiological update published by the World Health Organization on March 29, XE is estimated to be 10% more transmissible than BA.2, but the results require further confirmation.
The variant was first detected in the UK in mid-January, and since then, 600 cases have been reported in the country.
The UK’s Health Security Agency has stated that it monitors XE along with two other recombinants, XD and XF, which consist of the Delta and BA.1 strains.
UK health authorities clarified in late March that there was “insufficient evidence to draw conclusions about the growth advantage or other characteristics of this variant”, but addressed initial reports of infection.
“This recombinant, XE, has shown a variable growth rate and we cannot confirm whether it has a real growth advantage,” said Susan Hopkins, UKHSA’s chief medical advisor.
However, the recombinant variants themselves are not out of the ordinary, according to health officials.
“Recombinant variants are not unusual, particularly when there are many variants in circulation, many of which have been identified over the course of the pandemic thus far,” Hopkins stated. “As with other types of variants, most will die relatively quickly.”
The WHO said it would “continue to closely monitor and assess the public health risks associated with the recombinant variants” and would provide “updates as further evidence becomes available”.
