Japan detects first case of omicron XE variant

The health ministry announced Monday that Japan had for the first time detected the XE “recombinant variant” of the omicron strain of the coronavirus during a routine check at an airport.

The XE variant was detected in a woman in her 30s who arrived at Narita Airport from the United States on March 26. The woman, whose nationality was not immediately identified, was asymptomatic, the ministry said.

The XE strain is a recombinant of the omicron variant’s BA.1 and BA.2. subvariants. A recombinant variant occurs when an individual becomes infected with two or more variants at the same time, resulting in a mixing of their genetic material within the patient’s body, according to the U.K. Health Security Agency. As of April 5, England had reported 1,125 cases of XE, according to Japan’s health ministry.

According to the World Health Organization, early estimates based on limited preliminary data suggest that XE is about 1.1 times more transmissible than BA.2. However, the WHO has stressed that this finding requires further confirmation.

Hiroshi Nishiura, a mathematical modeling expert at Kyoto University, has said Japan should also keep an eye on XE and other new variants.

“XE’s transmissibility is certainly higher than that for BA.1 or BA.2,” Nishiura said last week. “If people’s international mobility increases, XE has a high chance of replacing the current omicron variants. But we still don’t know the severity of symptoms among the infected people, so we need to examine the epidemiological impact of the variant closely.”