ABSTRACT
On February 9th, 1998, a food poisoning outbreak occurred at a boarding school for underprivileged students. An unmatched case-control study was done. An environmental survey, laboratory study of rectal swab culture, fish-balls, water and the cooking utensils were also performed. There were 132 suspect cases, of which the attack rate in teachers was 9.8 per cent (4/41), 16.7 per cent (1/6) in the food handlers and 15.7 per cent (127/810) in the students. The median incubation period was 18 hours. Analysis of food consumption revealed those who ate lunch noodles had the highest risk (OR 3.8, 95% CI 0.6-5.9). In details of food components, those who ate fish-balls in curry had the only significant risk (OR 3.5, 95% CI 1.2-0.8) of becoming ill when compared to those who did not. Fish-balls in noodles and curry had a dose response relationship. Bacterial culture from 25 grams of fish-balls was positive for Vibrio parahaemolyticus. The fish-balls in noodles and curry were identified as the implicated food. The modes of contamination were uncooked food, cooking utensils and the food handlers. The manufacturer, which had no license to operate and had poor standards of sanitation, was closed by the Food and Drug Administration.