Japan’s capital of Tokyo is at the center of its coronavirus epidemic with more cases than any other region after a record number in a single day, data from public broadcaster NHK showed.

Tokyo registered a record 17 new cases on Tuesday, taking its tally to 171, and overtaking the hard-hit northern island of Hokkaido island as the prefecture with the most infections, NHK reported.

The outbreak has infected 1,214 people in Japan as of late Wednesday morning, with 43 deaths linked to the virus, NHK said. That excludes 712 cases from a cruise ship moored near Tokyo last month.

The International Olympic Committee and Japanese government on Tuesday agreed to put back the Tokyo 2020 Olympics to 2021 over the outbreak.

Tokyo’s new infections came after Governor Yuriko Koike warned that a lockdown of the capital was possible if it saw an explosive rise in cases.

Koike on Monday called on residents to exercise restraint to avoid a lockdown. She said the next three weeks were critical for whether Tokyo would see an “overshoot” – an explosive rise – in virus cases.

Hokkaido ended a state of emergency over its outbreak of the coronavirus, which saw 163 cases.

The outbreak has now infected more than 420,000 across 196 countries, according to a Reuters tally, with almost 19,000 deaths linked to the virus.

Reuters