BACKGROUND: In March 1999, six children who attended a nursery school became ill with acute gastroenteritis by Shigella sonnei. The majority of the children became sick one day after sharing a snack which was served from one of the children's home. By the time the outbreak of dysentery was recognized, the rest of family members of the children became also sick. The nursery school was located in a crowded residential area. EPIDEMIOLOGIC INVESTIGATION: After active and passive surveillance was established on patients with diarrhea, 438 patients were registered. Among them, 252 patients were considered to have simple diarrhea, but the rest (186 patients) suffered from more than three consecutive diarrheas. Shigella sonnei was isolated from 75 patients. The first attack rate was estimated at 50.0%, the second, 25.6%-34.3% and the third, 13.5%. The epidemic lasted for two months spreading further from person to person in the highly populous area. The active surveillance was implemented after the occurrence of the secondary attack of dysentery among the residents, who had no obvious direct contact with people associated with the nursery school. CONCLUSION: This investigation demonstrates the need for prompt implementation of active surveillance when Shigella infection is recognized in a highly populous city.
Child ; Diarrhea ; Dysentery* ; Gastroenteritis ; Humans ; Schools, Nursery ; Shigella ; Shigella sonnei ; Snacks