Health authorities in Japan are sounding the alarm about influenza, as the number of cases per institution rises in many parts of the country.

The National Institute of Infectious Diseases and other entities say about 5,000 medical institutions nationwide reported 117,652 flu patients in the seven-day period through Sunday.

The average number per institution was 23.93, up 1.31 from the previous week. The figures went up in 32 of Japan's 47 prefectures.

The figures surpassed the warning level of 30 in seven prefectures. By prefecture, the number was the highest in Fukuoka at 56.48, followed by Saga at 38.15 and Kumamoto at 34.83.

The figures in 37 prefectures exceeded the threshold of 10 for an advisory, with 29.56 in Osaka, 29.55 in Aichi and 22.83 in Tokyo.

Professor Hamada Atsuo of Tokyo Medical University said the number of flu patients is rising due to the spread of the type B virus. He added that flu infections are likely to reach a peak soon as the pace of spread is slowing down.

Even so, the professor called on the public to take measures to prevent the flu spreading, as infections may continue for some time.