The fatal norovirus epidemic at Yokohama Denentoshi Hospital has spread to about 112 cases as municipal officials struggle to track down the route of the infection, municipal officials said Monday.

Four elderly bed-ridden patients at the hospital have died since being infected by an outbreak of infectious gastroenteritis linked to the virus. A total of 82 patients, including the deceased, and 30 staff had been infected as of Monday morning, they said.

The Yokohama Municipal Government has done four inspections at the hospital to determine the infection route, they added.

Meanwhile, the Maebashi Municipal Government in Gunma Prefecture has said that a woman in her 90s died at a nursing home after suffering from similar symptoms and that norovirus was detected in her feces.