Infectious gastroenteritis caused by the norovirus has spread among children since December, a survey by the National Institute of Infectious Diseases showed Wednesday.
Outbreaks of norovirus gastroenteritis have occurred at nursing homes for the elderly nationwide, causing a number of deaths, and the institute said that infants can also develop aggravated symptoms.
According to weekly reports from some 3,000 pediatric clinics nationwide, the number of children with the disease was 14,500 during the week of Nov. 15 to Nov. 21, but rose to 37,000 in the week of Dec. 6 to Dec. 12.
The latest reports, for the week of Dec. 13 to Dec. 19, showed the number had further increased to 48,000.
Outbreaks of norovirus gastroenteritis are common in semiclosed environments such as hospitals, nursing homes, schools and cruise ships, according to Britain's Health Protection Agency.