The average number of new influenza cases for each regularly monitored medical institution in Japan stood at 14.90 in the week through Sunday, exceeding the alert level of 10, the health ministry said Friday.
The figure, based on data reported by about 3,000 of such institutions nationwide, surged from 6.29 in the previous week, surpassing the alert level that indicates a possible large-scale outbreak within four weeks.
Of Japan's 47 prefectures, 25 saw their average top the alert level, with the highest figure seen in Miyagi at 28.58, followed by 28.47 in Kanagawa and 27.91 in Saitama, approaching the warning level of 30. Their counts were followed by 25.04 in Chiba, 24.99 in Hokkaido, 23.80 in Okinawa and 23.69 in Tokyo.
A total of 2,307 kindergartens, nursery schools, and elementary, junior high and senior high schools have experienced partial or complete closures due to the flu.
Japan entered this year's flu season at the end of September, its second-earliest in the past two decades.
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