April 12, 2022
TOKYO – A novel coronavirus variant known as XE, which is believed to be more contagious than previous variants, has been detected in Japan for the first time, the health ministry said Monday.
XE was detected in a woman in her 30s who had been in the United States. She tested positive at a Japan airport on March 26.
According to the World Health Organization, the XE variant is a recombinant of the omicron subvariants prevalent in Japan: BA.1 and BA.2. It was first detected in the United Kingdom on Jan. 19 this year, with about 600 confirmed cases of XE as of March 29.
XE appears to have arisen after genetic recombination of the virus in a person who was infected with both omicron subvariants at the same time.
The new variant is said to be 10% more infectious than BA.2. Vaccine efficacy and the detailed nature of XE is not yet known, so further confirmation is needed, the WHO said.
“We don’t know the relation of the new variant to more serious symptoms,” Takaji Wakita, director general of the National Institute of Infectious Diseases and chair of a health ministry advisory panel, said April 6. “We need to keep conducting genomic analysis at quarantine.”
In Europe, more than 80 cases have been detected of the XD variant dubbed “deltacron” — a recombinant of the delta variant and the omicron BA.1 subvariant. The exact nature of XD is also unknown.
While deltacron has not been detected in Japan, Tetsuya Mizutani, a professor of virology at Tokyo University of Agriculture and Technology said, “Japan should have a surveillance system in place to contain the spread from overseas quickly.”