TOKYO (AP) – Japanese health officials confirmed dozens of new cases of swine flu in waves of announcements Sunday, as the government shut down schools and canceled community activities in affected cities.

Japan now has at least 78 cases, most of them teenagers.

Health officials confirmed some 70 domestic swine flu patients over the weekend. All tested positive for the H1N1 virus and were recovering in local hospitals or their homes.

Health and Welfare Ministry official Haruki Ogawa said the number could rise quickly with results on more viral sample tests imminently pending.

Hospitals have set up special “fever clinics” to separate possible swine flu carriers from other outpatients. Local governments established hot lines to guide people with flu symptoms. Newspapers also published graphics explaining the proper ways to wash hands and gargle.

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.

Japan’s first cases were believed to have been contracted outside the country.

The government immediately ordered schools closed in the affected areas.

“We have not determined how the virus spread in the region, and we are doing our best to track down the route of the infections and contain them,” Chief Cabinet Secretary Takeo Kawamura said.

Japan’s first four cases were spotted at an airport quarantine after three high school students and a teacher returned from a school trip to Canada in early May.

Officials said they did not know whether the first four cases were related to the latest outbreak.

“Many people were infected in such a short period of time,” Osaka Gov. Toru Hashimoto said at a news conference. “We must be prepared for a further expansion.”

The H1N1 swine flu virus is a new influenza strain.

Health officials have warned that it could eventually infect millions of people.

The World Health Organization has confirmed at least 8,480 human cases of swine flu in nearly 40 countries, mostly in the U.S. and Mexico, including 72 deaths.

AP-ES-05-17-09 1347EDT