The victims were among the 44 patients and staff who exhibited the virus-caused gastroenteritis symptoms of vomiting and diarrhoea at the hospital in Nichinan city, reported Xinhua citing hospital officials. The dead were all male patients aged between 78 and 88.
Norovirus infection is characterised by nausea, forceful vomiting, watery diarrhoea, and abdominal pain, and in some cases, loss of taste.
The hospital's director apologised for the delay in reporting about the norovirus outbreak. The authorities began suspecting norovirus when the number of patients rose sharply from four to 16 last week.
As norovirus outbreaks were also found in many other places recently, Japan's health ministry has urged local governments throughout the country to pay attention to the norovirus epidemic.