A Gastroenteritis Outbreak in a Military Hospital
1990 Vol.6 NO.12
On July 4, 1990, a food poisoning outbreak occurred among hospitalized patients in a medical care unit in a military hospital. One hundred eight-five patients became ill with diarrhea, abdominal pain, nausea, vomiting and sweating starting approximately at 8 a.m. A retrospective procedure was used to interview all patients in that particular building. A total of 295 questionnaires were collected, with 87 respondents complaining of some discomfort. A case was defined as a patient of the medical care unit in the military hospital with at least one of the major symptoms (diarrhea or vomiting) and one of the minor symptoms (abdominal pain, nausea, sweating, or fever). Eight-two patients met this criteria, five failed to meet the case definition and were discarded for further analysis. The attack rate was 45.6%. The 208 patients without complaints were used as controls. Analysis of returned questionnaires showed major symptoms of diarrhea (82.9%), abdominal pain (6&3%), nausea (45.1%), and vomiting (37.8%). Onset of disease clustered around one to seven hours after eating breakfast (see Figure 1). The median period of incubation was about 4 hours. Food items and statistical analyses of the cases and controls are summarized in Table 1. Two food items, bread and oat milk, were consumed at breakfast. A statistically significant difference in attack rates was found between cases and controls according to food item consumed (p <0.05 by a Chi-square test). Attack rates for those who ate the bread and who did not eat the bread were 45.7% and 1.7% respectively, with a relative risk as high as 26.9%. A large amount of Staphylococcus aureus was cultured from the bread, though no pathogenic bacteria were found in the vomitus. The bread was supplied by a local factory on contract, and the supply was suspended immediately. Most patients had recovered by the afternoon of the same day after receiving treatment.