Japan's health ministry announced Sunday that 20 more teenagers have been confirmed as having swine flu, as the government shut down schools in affected cities. The country's tally is now at 25.
The students, who attend several high schools in the western prefectures of Hyogo and Osaka, tested positive for the H1N1 virus over the weekend and are recovering at local hospitals, health ministry official Takuya Nemoto said.
The news of the rapid spread of the virus at schools came a day after Japan confirmed its first domestic case of swine flu in another student in the western port city of Kobe, about 270 miles (430 kilometers) west of Tokyo.
The students have not traveled overseas recently, but tested positive for the same strain that has killed more than 70 people worldwide, mostly in Mexico.