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Korean Journal of Epidemiology 1985;7(1): 44-58.
1984년7월 K병원 중환자실을 중심으로 집단발생한 비폐염성 Legionelliosis(Pontiac Fever)에 관한 역학적 연구
김정순, 이성우, 심한섭, 오대규, 조민기, 오희복, 우제홍, 정윤섭
An outbreak of Legionellosis (Pontiac fever) in ICU of K hospital, Korea
Joung Soon Kim, Sung Woo Lee, Han Soup Shim, Dae Kyu Oh, Min Kee Cho, Hee Bok Oh, Je Hong Woo, Yun Sop Chong
Abstract
Early in the morning of July 21,1984 three ICU patients out of eleven died within three hours, and also several medical as well as nursing staff working in ICU of K hospital became seriously ill. The hospital has about 500 beds and located in the middle of Seoul City with good reputation. The hospital started remodeling of the building from the middle of July with an extensive ground excavation to bury cables, particularly around the ICU. The hospital is furnished with central heating/cooling system but for some reason there was a box air-conditioning attached to the window facing to outside where the ground excavation was going on. An epidemiological investigation was carried out from July 25, 1984 in order to identify the entity of the outbreak by the governmental epidemiology team although the hospital insistingly incriminated the deaths of the ICU patients to their serious conditions and clustered occurrence of the illness among the staff to influenza-like croup. The epidemiologic investigation consisted of interview and blood collection for the ICU staff, medical record reviews for the deceased, and environmental survey of the hospital including the ICU. Also an additional study was conducted following the initial study from which legionellosis was suspected as the cause of the outbreak; the interview survey was extended to the entire nursing staff of the hospital, medical record review to all ICU patients and specimen collections for the agent isolation such as water collection from tap water, cooling tower of the central cooling system and the box air-conditioning, and dust from the ICU and its vicinities. Unfortunately, however, any autopsy of the deceased was not performed because they had been hurried already when the investigation started; also the effort of the team to collect blood specimen for the serological test from the ICU patients discharged and the entire nursing staff interviewed failed due to hospital’s reluctance for the additional study. Therefore the investigation had to rely upon the interview survey on the whole nursing staff in identifying the focus of exposure to the legionella and the serological test results on ICU staff only. In order to confirm the peculiarity of the outbreak to that particular place, ICU of K hospital, the ICU nursing staff of S hospital located in Seoul were also interviewed and serologically tested. The results of the epidemiological investigation summarized are as followings: 1) The clinical and epidemiological characteristics of the illness that had occurred among the ICU staff were so typical that there was no alternative to consider but non-pneumonic legionellosis (pontiac fever). 2) There were 23 legionellosis patients diagnosed clinically among 26 hospital staff who had been exposed to the ICU environment more than two hours during 32 hour-period between 08 hour of July 19, 1984 and 24 hour of July 20, 1984 ; the attack rate was 88.5%. 3) In serological test by means of IFA test on paired sera against antigens of fourteen serogroups, 14 person’s sera out of 19 reacted positively only against the antigen of L. gormanii. Two out of 14 clinical legionellosis reacted negatively, and two persons out of five healthy staff exposed showed positive results. Accordingly inapparent infection rate among positives of the serological test was 14.3%. The infection rate based on result of serological test among those who were exposed to the ICU during the estimated duration of Legionella contamination and serologically tested (17 persons) was 94% ; one nurse whose serological test revealed negative had serious and typical feature of legionellosis clinically. 4) The most frequent symptoms of the non-pneumonic legionellosis among serologically confirmed cases were fever (100%), malaise (92%), chills (83%), headache (83%), generalized myalgia (83%), and anorexia (83%). The duration of the illness was 2~3 days in most of the cases. 5) The expired three patients in the early morning, July 21, 1984 with admission diagnosis of bleeding gastric ulcer, liver cirrhosis and acute myocardial infarction had abnormal chest X-ray findings; one with increased density on RLL and two with pulmonary edema before the death. Among seven survivals who had been exposed to the ICU environment during the risk period five patients had revealed abnormal chest X-ray, two of them with definite pneumonia. 6) The duration of exposure to the Legionella contaminated environment estimated from the association between the disease occurrence and the time of exposure was most likely from around midnight of July 19 to that of July 20, 1984. 7) The incubation period that was estimated from the duration of exposure and onset time of the illness ranged from 20 hours to 42 hours. 8) The clinical pathological laboratory results between serology positives and negatives revealed no difference except the CBC; electrolyte, liver and kidney functions were all within normal limits, however, about the half the confirmed cases showed leucocytosis with relative increase of segmented white cells and lymphocytes. 9) The interview survey on clinical manifestation of the illness for all nursing staff of the hospital showed prominant clustering at a point of time only for the ICU staff, which, implies the occurrence of the legionellosis was peculiar to the ICU within the hospital. The interview and serological survey on the same illness during the same period for the ICU nursing staff of S hospital located in Seoul as a control yielded negative results of serological test against the L. gormanii. One of ten nurses, however, showed 1 : 128 antibody titer to L. pncumophila serogroup 1 suggesting there had been sporadic legionella infection in Korea although this is the first report on legionellosis outbreak in Korea. 10) The effort to isolate the legionella organism from water and dust specimens collected in ICU itself and its vicinities was failed; probably well-planned experiment such as aerosol exposure of guinea pigs with water from box airconditioner and the soil extract from the ground excavated might have produced positive results. 11) It was inferred that the source of ICU contamination by the Legionella could have been the box airconditioner attached to the window outside of which an extensive ground excavation was going on to bury cables; L. gormanii had been aspirated to the airconditioner, multiplied in the water of airconditioner, and aerosol sprayed into the ICU.


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