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M.Y Ahn 2 Articles
Epidemiologic characteristics of leptospirosis and febrile disease in population in special service at high risk of infection
Joung Soon Kim, Yong Heo, H.W Chung, W.Y Lee, H.G Byun, J.D Suh, C.M Sung, M.Y Ahn, J.M Choi, S.J Lee, Y.C Hahn
Korean J Epidemiol. 1987;9(2):278-287.
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Abstract
This is a part of serial works on leptospirosis. In this study, a correct characterization of all of the hemorrhagic disease accompanying high fever which might be caused by various agents such as leptospira, rickettsia, viruses, and others if any was attempted by classifying the symptoms and identifing the etiologic agent which is responsible for the cases. And also serologic studies along with fundamental epidemiologic investigation on the clinical signs of the patients selected from the study area were done to draw a comprehensive conclusion. The specific aim which is the major focus of this part of study is to find out prevalence rate of true leptospira patients among patients with high fever and to characterize the clinical pictures, such as clinical signs and symptoms, which might be specific for the true cases of leptospiral infection which is confirmed by bacterial isolation from the cases. One hundred and nineteen patients hospitalized because of high fever (more than 38°C) for more than 24 hours were studied during 10 month (Aug., 1986-May 1987). The findings are summarized as follows; 1) At the time of admission, leptospira isolation rate was 5.8% (6/103) and this became 13.7% (7/44, average 8.4%) after one week of hospitalization. 2) The serum samples were testeded for the presence of the antibodies specific to 22 different servar in which 3 strains isolated in this laboratory from human blood employing microagglutination tests. The positive rate was 34.9% when the first blood samples which were collected at the time of admission tested. And it became 50.9% when the second samples were tested one after the first. The antibody conversion rate within one week was 32.4%. Only one out of 16 cases who were antibody positive at the first test was found to be negatively converted. When these were grouped by their antibody titer, 83.7% of whole antibody positive samples (64) demonstrated antibody titer 1.400 or lower and only 3.1% of them demonstrated higher than 1:3200. 3) Significantly higher positive rate were found when the sera were tested with the fresh strains isolated from that area. The majority (32.4%) of the sera from Chullwon area positively reacted with locally isolated L. icterhemorrhagiae lai and 17.1% of sera from Yangoo area with locally isollated L. canicola. In Chullwon area, 65% of the serum samples were identified belonging to 3 serovars, L. icterohemorrhagiae lai (32.4%), L. canicola (14.7%), and L. ictervhemorrhagiae copenhageni (17.6%). In Yangoo area, 54% of the scrum samples were positive for 4 serovars, L. icterohemorrhagiae lai (14.6%), L. hebdomadis (12.2%), L. icterohemorrhagiae copenhageni (9.8%) and above mentioned local isolate. 4) among 92 patients with high fever 19 cases (20.2%) were confirmed to be leptospiral infection by the both tests for bacterial isolation and serology. Sixteen cases (16%) were the suspicious cases of leptospirosis. The rest of them, 60 patients (63.8%) were found to be uninfected with the bacteria. 5) When the seasonal changes of incidence of the feverrile disease were comparatively analyzed, the cases belonged to confirmed as leptospirosis occured maily in Autumn whereas the others occured throughout the year except the spring in which time a slight decreased cases were recorded. The incidence of the confirmed cases were higher in groups which had been exposed to field trainings. Sore throat, runny nose, hematemesis, and muscle pain were found to be significantly frequent signs complained by the confirmed cases and diastolic blood pressure of the cases was higher. 6) amomg the confirmed cases only 5.3% of them were primarily diagnosed as leptospirosis and majority were diagnosed as fever with unknown reason (47.3%) when they were adimitted because of the high fever. Whereas among the cases confirmed as uninfected 25% was fever with unknown reason and 46.7% for the others. The proportion of cases diagnosed as leptospirosis was 5.0%.
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Key Message
An epidemiological characteristic of dysentery outbreak in a rural area
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
Korean J Epidemiol. 1986;8(2):330-336.
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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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Epidemiol Health : Epidemiology and Health