Omicron Subvariant Ba.5 Found To Be 27% More Contagious Than Ba.2
A group of researchers in Japan says the Omicron subvariant BA.5 is 27 percent more contagious than the BA.2 subvariant, which has been the main cause of the country's recent coronavirus infections.
The group led by Professor Nishiura Hiroshi of Kyoto University and Professor Ito Kimihito of Hokkaido University submitted the report to a meeting of an expert panel of Japan's Health Ministry on Wednesday.
The group says that it assessed the transmissibility of the Omicron subvariants BA.2 and BA.5 based on the results of PCR tests conducted in Tokyo.
The BA.5 subvariant has been rapidly replacing the BA.2 subvariant around Japan.
The group says the reproduction rate, or the "R" value, of the BA.5 subvariant was estimated to be 27 percent higher than the BA.4 subvariant.
The value refers to the average number of people that one infected person will spread the virus to.
Regarding the BA.4 subvariant, which has been spreading widely outside Japan, the group says its R value was estimated to be 71 percent higher than that of the BA.2 subvariant. But the group added that the number of samples it had was so small that they could not make a decisive assessment.
Professor Nishiura says the BA.5 and BA.4 subvariants have similar levels of transmissibility and the two spread together in South Africa.
He says it remains unknown which would prevail in Japan, and that how infections spread needs to be watched closely.