一起SARS暴发传播链的调查分析

目的 分析SARS暴发案例的传播特点,评价SARS在发病前后的传染性。方法 以一起主要发生在北京的SARS暴发为研究对象,采用回顾性调查的方法,用统一的调查表,以现场调查和电话调查相结合的方式对275例接触者进行线索追踪和个案调查。用传播链示意图分析传播关系,用接触史分析图分析传染性。结果 本起SARS暴发传播链中的接触者275人,发病41例(不包括先证者),死亡5例,罹患率14．9％,病死率12．2％。其中家族病例19例(占46．3％),单位聚集病例13例(占31．7％)、社区病例8例(占19．5％),私人诊所医生1例(占2．4％)。其传播过程可用传播链清晰地描述。41例病例均与前代病例的症状期有密切接触史;仅与前代病人潜伏期接触的114人无一人发病;未发现无症状的密切接触者有传染性。无防护地照顾护理病人最危险,其次是一起居住、看望病人和给SARS病人看病。本案例的潜伏期为1～10d,中位数为3d。结论 全部SARS病人在发病前均与其前代病例症状期有过密切接触;传染性的强弱与SARS病人与密切接触者的接触方式有关;未观察到SARS病人潜伏期有传染性。

Epidemiological study of the transmission chain of a severe acute respiratory syndrome outbreak

OBJECTIVE: To investigate the process of SARS transmission and to evaluate infectivity of SARS patients in different periods of disease development. METHODS: A case of SARS outbreak beginning from a male, 74-year-old patient in Beijing. Two hundred and seventy five primary, secondary and tertiary contacts, including family members relatives, colleagues, and others exposed to him, were traced by field investigation and telephone interview using a standardized questionnaire. The transmission process and infectivity of disease were analyzed with transmission chain diagram and contact history diagram. RESULTS: Among the 275 contacts of the index case, 41 fell ill of SARS with an attack rate of 14.9% and 5 deaths with a fatality rate of 12.2%. The transmission chain of this outbreak could be clearly delineated, and all the 41 cases had close contacts with their infectors, SARS cases of the previous generation within the symptomatic period thereof. All of the 114 contacts that contacted their infectors, SARS cases of the previous generation during the incubation period thereof remained healthy. The incubation period of 27 cases that had contacted their infectors only once was 1 - 10 days with a median of 3 days. The highest risk of being infected was caring the patients unprotectedly, followed by living together with patient, visiting patient, and handling patient without protection. CONCLUSION: All the secondary cases have the history of close contact with their symptomatic infectors of previous generation. It cannot be proved at all that SARS is infective during the incubation period. The infectivity of SARS is related to the degree of closeness of contact with the patient.