In May 2008, a diarrhea outbreak occurred among students of in a girls' high school (S school) in Sangju-si, Korea. An epidemiological investigation was carried out to clarify the cause and transmission route of the outbreak.

S school has been providing meals directly since July 2007. We conducted a questionnaire survey among 591 persons, and examined 283 rectal swabs and 98 environmental specimens. The patient case was defined as a member of S school who had diarrhea more than one time in a day, accompanied with one or more symptoms among abdominal pain or tenesmus from May 19th to May 26th 2008.

The attack rate was 24.0%. Bacillus cereus were cultured from three of the rectal swabs and five of the preserved foods. It was suspicious that contamination was possible in seasoning vegetables, and we found some foods were seasoned with spices after being cooled by moving cooler for about 20 minutes. Enterotoxin positive B. cereus were cultured from two foods cooled by moving cooler. Enterotoxin negative B. cereus were cultured from two environmental specimens of the moving cooler.

We presumed the cause of the diarrhea outbreak in S school was food poisoning by B. cereus . Because enterotoxin positive B. cereus were cultured from rectal swabs and foods, and the symptoms were corresponded. We estimated the outbreak was occurred by this process that B. cereus in the moving cooler contaminated foods during cooling and then rapidly proliferated.