The National Institute of Infectious Diseases reported that the number of people who visited medical institutions designated to observe the flu situation totaled 3,688 during the week through Sunday, or 0.77 per institution -- falling below one for the first time since early August.

The outbreak peaked in the week of Nov. 23-29, when the per- institution figure came to 39.63 three months after the health ministry declared that an epidemic of the new H1N1 strain of influenza A had fully begun in Japan.

The data were collected from about 5,000 medical institutions picked for the institute's weekly flu reports. Most of the cases in the latest reporting week are believed to be H1N1, according to officials of the institute.

Based on its weekly surveys, the institute estimates the number of people who have contracted flu since last July has reached 20.63 million in Japan.

Health, Labor and Welfare Minister Akira Nagatsuma said his ministry will remain on alert for the next wave of flu outbreaks.

"It cannot be denied that the second wave of outbreaks won't come, so we'll continue to closely watch how the situation develops," he said.