An Epidemiologic Investigation of Shigellosis Outbreak in Gangnung 1998

Jung, Sang Hyuk; Park, Woong Sub

Abstract

An epidemiologic investigation was carried out to identify the distribution and the cause of Shigellosis outbreak, which was occurred in Gangnung city from August to November, 1998. This study carried out from September, 14, to November, 20, 1998. The total number of Shigellosis confirmed patient is 87. We surveyed and obtained the stool sample from all suspected patients and their members of household. The major findings of this study are as follows. 1. The first patient appeared in September 11 and the number of patients increased to September 13, that is peak time, and the patient number tailed down apparently from September, 18, 1998. 2. The incidence rate per 1,000 is largest in Wangsan-Myeon Doma-Ri(32.9), and second largest in Wangsan-Myeon Mokgea-Ri(31.6), The total incidence rate in Gangnung-shi is 0.4(0.4 for man and 0.3 for woman). The age group with the largest incidence rate per 1,000 is 5-14 age group whose incidence rate is 1.4. 3. The secondary generation attack rate in confirmed patient family is 20.6%, and the secondary attack is 7.8%. 4. We considered the meal of school, environmental factor, milk, carrier of Shigellosis as the cause of outbreak, but we were not able to identify the bacteria of shigellosis. But we suspected the meal of school that played important role in outbreak, because outbreak occurred explosively after students ate the meal of school. 5. We considered three hypotheses for the cause of the outbreak. First, a propagation from external regions; Second, an outbreak from contaminated foods; Third, a propagation from carriers in Gangnung. In order to obtain the further information for first and third hypothesis, we should perform PFGE(Pulsed-field gelectrophoresis) with the shigella bacteria of each epidemic region.