Four patients have died at a Yokohama hospital after an outbreak of infectious gastroenteritis left nearly 100 patients and medical personnel ill, some with signs of the norovirus in them.

Officials at Yokohama Denentoshi Hospital said Saturday that two male patients aged 80 and 92 and two female patients aged 95 and 97 died of breathing problems and pneumonia after signs of vomiting and diarrhea.

Another 68 patients and 27 staffers have been suffering from gastroenteritis since Tuesday, the officials said.

In a separate case earlier this month, one of eight patients infected by a norovirus outbreak at a hospital in Matsuyama, Ehime Prefecture, died of multiple organ failure, hospital officials said.

The 88-year-old man died on Dec. 6 after coming down with diarrhea on Nov. 24 and being diagnosed with a norovirus infection on Dec. 1, they said.

On Dec. 4, the Ehime hospital confirmed that the other seven also had norovirus infections but said none was critically ill.

The hospital, however, declined to report the outbreak to the city health department after concluding on Dec. 10 that it had been contained, the officials claimed.

The Health Ministry warned municipalities nationwide in late November about a spreading norovirus epidemic after suspected cases of infectious gastroenteritis caused by the norovirus were observed at their highest pace since 2006.