This electron microscopic image provided by the Chinese Center for Disease Control and Prevention and GISAID (Global Initiative on Sharing All Influenza Data) shows the new coronavirus.

TOKYO -- A sudden spike in new coronavirus cases was confirmed among attendees at a New Year's party for independent taxi drivers held on a traditional "yakatabune" river tour boat in the capital.

The Tokyo Metropolitan Government says the virus may be spreading in the capital, as people not at the party -- including an office worker and a chauffeur -- were also confirmed infected, and is calling for measures to prevent transmission. It provided information on the route of infection among party attendees at a Feb. 16 press conference.

The New Year's party was held on Jan. 18 by a branch of a private taxi union based in Tokyo's Jonan area, and was attended by about 70 taxi drivers and their families who dined on the boat. However, the windows were shut due to heavy rain, creating a confined space with insufficient ventilation -- the kind of environment where disease spreads more easily.

The metropolitan government has been conducting tests on around 200 people involved in the party, on the assumption that the infection had spread on the yakatabune boat.

An independent taxi driver in his 70s, who participated in the party along with his wife, had tested positive in Tokyo. He is the son-in-law of a woman in her 80s from Kanagawa Prefecture, south of Tokyo, who died on Feb. 13 -- Japan's first confirmed fatality from the COVID-19 illness.

The metropolitan government began investigating in the wake of the woman's death, and had confirmed 11 participants and yakatabune employees were infected with the coronavirus as of Feb. 16.

Two people who were not onboard the tourist boat also tested positive for the new virus: a female employee with the union branch in her 50s, who had contact with the taxi driver at work, and a doctor in his 60s at Makita General Hospital in Tokyo's Ota Ward.

A nurse at the hospital who tested positive for coronavirus on Feb. 15 had attended the New Year's party as a family member of one of the taxi drivers. The doctor had dined with the nurse along with other people on three occasions in late January.

(Japanese original by Koichi Uchida and Yoshikazu Takeuchi, Tokyo City News Department)