WHO records new SARS-CoV-2 variant

XE recombinant reported in the U.K.

The World Health Organization (WHO) has flagged the emergence of a new variant of the SARS-CoV-2 virus, the XE recombinant, in the United Kingdom, and with a possibly higher rate of transmission.

The WHO, in its weekly epidemiological update, said the recombinant was detected in the United Kingdom on January 19 and over 600 sequences have been reported and confirmed since. It went on to add: “Early-day estimates indicate a community growth rate advantage of about 10% as compared to BA.2, however this finding requires further confirmation.”

The U.K. Health Security Agency (UKHSA), which tracks SARS-CoV-2 variants, analysed three recombinants, known as XF, XE and XD. It explained that, of these, XD and XF are recombinants of Delta and Omicron BA.1, while XE is a recombinant of Omicron BA.1 and BA.2. A recombinant variant occurs when an individual becomes infected with two or more variants at the same time, leading to a mixing of genetic material in the human body. Several such recombinants have emerged in the past during the pandemic.

The UKHSA has stated that in the U.K., only 38 cases of XF have been identified, though none since mid-February. There is currently no evidence of community transmission within the U.K. XD has not been identified in the U.K. to date, though 49 cases have been reported to global databases.

However, a total 637 cases of XE have been confirmed in the UK so far. “The earliest of these has a specimen date of 19 January 2022. There is currently insufficient evidence to draw conclusions about growth advantage or other properties of this variant,” the agency said. However, all the recombinants are being tracked closely, it added.

Reflecting this, the WHO also said that until there emerges further confirmation on the community growth rate, “XE continues to belong to the Omicron variant until significant differences in transmission and disease characteristics, including severity, may be reported.” It has also committed to closely monitoring and assessing the public health risk associated with the recombinant variants.