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An epidemiological characteristic of dysentery outbreak in a rural area
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Y.H Kim, S Bang, J.S Kim, Y Heo, H.K Chung, M.Y Ahn, J.K Lee, C.I Ku, H Kim, S.M Kwon, W.H. Chang
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Korean J Epidemiol. 1986;8(2):330-336.
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 Abstract
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Abstract
In the middle of August 1986, several people in a small rural village(179 residents) had a similar disease that was characterized by watery diarhea, crampy adominal pain, fever and vomiting. On this outbreaks, local health department collected stool specimens for culture and administered antibiotics prophylactically. From ten stool cultures the Korean National Institute of Health isolated two strains of Shigella flexneri.
Even after the massive prophylactic administration of antibiotics, the occurrence of the cases did not show any change. Therefor the community health program of Soonchunhyang medical school and the health department in the area devided to conduct an epidemiological investigation jointly with the team of Seoul National University, in order to find epidemiological characteristics of the outbreak.
Followings are the results summarized:
1) Five strains of bacteria isolated and identified independently by three different institutes, two strains in Korea NIH, two strains in Seoul National University and one in local hospital, were all Shigella flexneri, which confirmed the cause of the outbreak being Shigella flexneri.
2) Incidence rate of the bacterial dysentary among 163 population in 41 households was 35%. It was not significantly different by age group and sex.
3) On the study of environmental factors such as water supply, sewer system, struction of privy, and communal dinning and etc. to explore a possible common source of infection, no such factor assciated with the outbreak was found.
4) Familial aggregation statistically examined by binomial distribution revealed strong(p< 0.005) association. Age and sex specific incidence rate of index cases was significantly high in female old aged(over 60 years of age), suggesting that the dysentery primarily spread by grand-mothers visiting around neighbours.
Thus it was concluded that this dysentery has spread insidiously in a small rural village through person-to-person transmission by intimate association between neighbours, particularly by old aged females.
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Summary
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An epidemiological study on subclinical Leptospiral infection among rural Koreans by Leptospira isolation in blood culture
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Joung Soon Kim, J.K Lee, H.W Chung, S.J Yang, H.S Lim, W.Y Lee
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Korean J Epidemiol. 1985;7(2):253-258.
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Abstract
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Abstract
A clinical syndrome complex that had been known as epidemic pulmonary hemorrhagic fever in Korea since 1975 has been proved to be leptospiral infection by Kim et al. in 1984.
Even though hundreds of cases have been reported for the last 10 years, few information on the status of leptospiral infection among general population at risk is available.
This study was carried out in a small rural community with 189 population in 41 household to estimate subclinical leptospiral infection rate. The study consisted of interview, medical examination by doctors, and blood sampling. The first study in which only 50 inhabitants completed the study on November 3rd, and the second one for the drop-outs on December 17th, 1985.
The blood specimens were inoculated to a newly developed artificial media by Lee, YUMC-5050, which had been demonstrated to be quite sensitive, silver stained in two weeks of culture and examined under microscope for the characteristic leptospiral bacteria. Since leptospiral positives were found only among the first study group, probably due to the optimal timing for culture (November 3rd), but none of 40 specimens sampled in the second study was culture positive, the data analysis had to be depended upon the first study population. Among six positives re-cultured in the second study period, only one remained positive and five became negative within one and half month.
The summarized findings are as followings：
1) Leptospira culture positive rate was 16% average; 23% for males and 11% for females. The cases were net clustered to any particular age group but rather even for all active ages. Protective immunity for older ages was not evidenced.
2) Clinical symptoms and signs experienced by the study subjects during the last one month were not significantly different in kind and frequency between leptospira positives and negatives except one case each for hematuria and lymphadenpathy in positive group. Two out of eight positives had mild clinical manifestation competible to leptospiral infection but six of them were typical of subclinical infection.
3) Enviromental factors exposed also were not different between leptospira culture positives and negative, probably owing to the fact that these farmers were exposed to all environments in multiplicity making it difficult to find out the difference for any environmental particulars.
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