The number of COVID-19 infections in Tokyo may have jumped nine-fold since last summer, antibody tests show, as Japan tries to rein in its third and most lethal coronavirus wave ahead of the Olympics.
Random testing on people in Japan's capital in December showed 0.91 per cent had antibodies to the virus, compared with about 0.1 per cent in a similar study in June, health ministry said in a report on Friday
The study sampled more than 15,000 people and also showed increases in antibody rates in Osaka and Miyagi Prefecture.
Reported infections in Japan have trended down in recent days but the government has signalled it will remain cautious.
Japan last month imposed a one-month state of emergency for 11 areas, including Tokyo, neighbouring prefectures and the western city of Osaka.
It had decided to extend the emergency in 10 of the 11 prefectures until March 7, as the medical system remained under pressure despite a decline in the number of cases.
The country has had more than 390,000 cases of the coronavirus and 5832 deaths.
It is desperate to stamp out flare-ups of infection as it prepares for the summer Olympics, due to begin on July 23.