一起传染性非典型肺炎爆发的“超级传播者”和传播链分析

目的：了解严重急性呼吸综合征(SARS)爆发案例的传播过程，分析SARS病例不同阶段的传染性和不同接触方式的危险性。方法：设计统一调查表，用查阅病历、面对面调查和电话调查相结合的方式进行，以指征病例为起点进行线索追踪和个案调查。用传播链示意图分析传播关系，用接触史分析示意图分析传染性。结果：共追查到与该案例传播链相关的接触者207人，发病36例，死亡1例，总罹患率为17％。其中指征病例和1名二代病例分别直接传播了12例和13例续发病例，其传播过程可以用清晰的传播链加以描述；所有36例病例均与前代病例的症状期有密切接触史，家族传播链中85％的病例都与前代病例症状期的第3—5天有过接触，发病前后均接触和仅发病后接触者罹患率分别为70％和67％，差异无显著性；仅与前代病例潜伏期接触的15名同柜台同事、29名同班同学无发病，38名与医护人员发病前或发病初期密切接触的家属无发病。结论：该案例所有的续发病例都有与症状期病例密切接触史；未观察到SARS患者在其潜伏期内存在传染性。

Analyses on one case of severe acute respiratory syndrome ‘super transmitter' and chain of transmission

Objectives To investigate the transmission process of severe acute respiratory syndrome (SARS) and to evaluate the infectiveness of SARS patients in different periods of disease epidemics. Methods Standardized questionnaire was used to conduct case investigation and contact tracing by combining the field investigation and telephone interview. Transmission process, infectivity, transmission chain and contact history of SARS were studined through data analyses. Results On 25th March 2003, a 91 year old man was admitted to Hospital J in Beijing with stroke and fever. He died on 30th March. From 31st March, there was an outbreak of SARS among his contacts in the family and in the hospital he was admitted to. Contacts would include his relatives,other co-patients and health care workers in the Hospital J. Chinese Field Epidemiology Training Program trainees conducted an investigation of the outbreak. Among the 207 contacts of the index cases through different generations, there were 36 cases of SARS (attack rate 17%) patients with one death. There were 12 cases having directly contact with the index case and 13 cases with one secondary case. The transmission chains of this outbreak could clearly be depicted. All the cases had close contacts during the symptomatic period of their index patients. Among the relatives, 85% of the cases had 3-5-day contact with their index patients after the onset of the illnesses. There was no significant difference between the two attack rates-70% for whose who had contact with the patient before and after illness onset) and 67% for those who only had contact after the onset of the illness. Out of the 44 social acquaintances and 38 of the family members who had contacts with the index patients during the incubation period, no one was found ill. Among the close contacts at the hospital who had no protection when providing care to the patient, the attack rate was found over 80%. Conclusions All the secondary cases of this outbreak had a history of direct and close contacts to the index patients after the onset of the illness. There was no evidence indicating that SARS cases were infectious during their incubation period.