Epidemic curves and interventions. a) Epidemic curves and interventions of attached schools in districts A and F. Arrows indicates the periods of class closures (a and c) and a school closure (b). Each class closure ranged from 1 to 10 days, with some classes closed simultaneously. Kindergartens, elementary schools, and junior high schools in district A were closed simultaneously for 4 days, but only once. b) Epidemic curve and interventions of club closures (d) among university students. Club activity was stopped when more than two attendees were infected at the same time. Some clubs were closed simultaneously in October and November 2009, and the number of patients decreased after the interventions.