TOKYO (Kyodo) -- The number of infectious gastroenteritis cases caused by norovirus and other pathogens in Japan hit the highest level in 10 years in the week through March 16, according to recent data from the public health institute.

Reported by designated medical institutions nationwide, the total figure reached 34,609, with the average standing at 11.1 over the annual seven-day survey period, the National Institute of Infectious Diseases said.

The Ministry of Health, Labor and Welfare has urged thorough handwashing, saying, "People with weak immunity, especially children and the elderly, should be careful to fully cook foods that require heating before eating them."

Gastroenteritis from norovirus causes repeated vomiting and diarrhea, usually resolving within a day or two. Infections, however, can lead to dehydration in young children and the elderly, which can exacerbate underlying health conditions.

Humans can contract norovirus by eating contaminated oysters or inhaling particles near dried vomit from infected people. The virus is highly contagious and often spreads in daycare centers, kindergartens and schools.