A new coronavirus variant that could be the most transmissible yet has been identified in the United Kingdom. The variant, known as XE, is a combination of the omicron subvariants BA.1 and BA.2. It was first detected in the U.K. on Jan. 19, according to the World Health Organization, though it has since been reported in India as well. As of late March, roughly 600 cases of it were identified.