TOKYO: A gene analysis by a Japanese university has found that the dominant form of the omicron coronavirus variant and the emerging BA.2 subvariant showed no clear difference in symptoms.

The analysis released by International University of Health and Welfare showed that all cases with the BA.2 omicron subvariant who were diagnosed at an affiliated hospital developed no or mild symptoms.

The university analyzed genetic information on 92 cases who tested positive for the virus at the hospital in Narita, Chiba Prefecture, east of Tokyo, between December last year and mid-January this year.

The omicron variant accounted for 86 cases, of which 22 cases had the BA.2 subvariant. BA.2 was detected chiefly in people who entered Japan from countries including the Philippines and India.

Of the BA.2 cases, some unvaccinated people were asymptomatic while there were vaccinated people who developed symptoms such as sore throat or coughing, the university said.

The BA.2 subvariant appears to have no clear difference from the dominant BA.1 omicron strain in that many of those infected with it do not develop severe symptoms, the university said.

Some analysis has shown that the BA.2 subvariant is 18 pct more infectious than the BA.1 strain. In some countries, the BA.2 strain is becoming dominant.

In Japan, 318 BA.2 cases had been detected at quarantine stations as of Wednesday, health ministry officials said. BA.2 cases have also been identified by testing in various parts of Japan, suggesting that the subvariant may be already spreading in communities.

JIJI Press