Pandemic influenza (H1N1) situation report in Japan - update 16
October 2, 2009


Domestic situation in Japan

According to the National Epidemiological Surveillance for Infectious Diseases in Japan, the numbers of reported cases of the Influenza like Illness (ILI) have been increasing in the 38th epidemiologic week (September 14-20, 2009) (Figure 1). The number of cases reported per sentinel* in Japan was 4.95, which has increased compared to previous week (3.21 per sentinel). Based on this number, newly diagnosed ILI patients during this week are estimated to be approximately 270,000 (95% Confidence Interval 230,000-300,000) nationwide.


Okinawa Prefecture had the highest reported cases per sentinel (12.52), followed by Tokyo (10.24), Osaka (9.21). The numbers are increasing in most prefectures except for Okinawa, where the peak was recorded on week 35 (36.00).

According to the School absenteeism surveillance  report from Ministry of Health Labor and Welfare (MoH), in week 37, 166 schools throughout the nation have been suspended their all classes due to the influenza A (H1N1) 2009 epidemic in school. In addition, one grade was suspended in 500 schools and 2,840 schools have suspended a individual class with multiple infected students.




There were 152 reported hospitalization cases due to pandemic influenza A (H1N1) infection during September 16 to 22, according to MoH.

According to Infectious Agents Surveillance Report, most of the influenza cases detected/isolated during the week 19 through 39 were pandemic influenza A(H1N1) virus.

* The number of sentinel clinics and hospitals is decided depending on the relative population of the jurisdiction of each public health center and on consideration enabling statistical estimation of the incidents in the whole area of the prefecture. The influenza sentinel medical institutions consist of approximately 3,000 pediatric hospitals/clinics and 1,800 internist hospitals/clinics around the country.