深圳市某小学一起不明原因发热暴发现场的流行病学调查

Epidemiological Investigation of Outbreak of Fever of Unknown Origin in A Primary School in Shenzhen City

目的了解某小学不明原因发热的疫情特征,探讨其危险因素、传播模式和病原体,制定控制措施。方法制定病例定义:临床病例发热≥37.5℃、扁桃体肿大,并有咽痛、乏力、咳嗽、头晕、头痛、畏寒、皮疹症状之一者。开展病例对照研究和回顾性队列研究,用血平板及生化实验进行细菌培养及鉴定,用PCR进行流感检测。结果共搜索43例发热病例,罹患率为3.3%(43/1313),发病高峰在5月15日;主要临床症状为:100%发热和扁桃体肿大、97.7%咽痛和乏力、9.3%出现皮疹、咳嗽和头晕、7.0%出现畏寒、4.7%出现头痛;58.1%病例集中发生在二年级一班,该班级的罹患率为45.5%。病例对照研究:和病例接触是危险因素(OR=5.23,95%CI=1.20～28.38),进食前洗手是保护性因素(OR=0.22,95%CI=0.05～0.82)。实验室检验:鉴定病原体为!-溶血性链球菌,在对照人群没有培养出优势菌株,流感病毒PCR检测均为阴性。结论经过流行病学调查、临床表现和实验室检测,可以确定此起小学发生不明发热的暴发由!-溶血性链球菌引起的。因此控制措施的重点应为培养学生进食前洗手、定期更换牙刷等良好的卫生习惯;落实学生晨检制度,及时发现、及时隔离和治疗病例,从源头上预防疾病的发生。

Objective To find out the epidemic characteristics of fever of unknown origin（FUO） in a primary school, to explore its risk factors, route of transmission and pathogen so as to establish disease control measures. Method Clinical cases of fever （≥38℃） with tonsil swelling and any one of the following symptom： angina, fatigue, cough, dizziness, headache, intolerance to cold and rash were identified as fever of unknown origin. Casecontrol studies and retrospective cohort studies were conducted in the classes with relatively higher incidence rate. Bacteria strains were identified by blood agar plate culture and biochemical tests. Flu virus was detected by PCR. Result 43 cases of FUO were found. The incidence rate, which peaked at May 15th, was 3.3%（43/1313）, and then decreased rapidly in the following days. The major clinical symptoms included： fever and swelling of tonsil （100%）, angina and fatigue（97.7%）, rash, cough and dizziness（9.3%）, intolerance to cold（7.0%）, headache （4.7%）. 58.1% （25/43） cases were found in class 1 of grade 2, with an attack rate of 45.5%. The case-control study showed that contacting with FUO patient is the risk factor of come down with FUO （OR=5.23, 95%CI=1.20- 28.38）; washing hands before eating can prevent having FUO （OR=0.22, 95%CI=0.05-0.82）. The laboratory test showed that a-hemolytic streptococcus instead of pneumococcus was identified from 6 specimens of cotton swabs of 6 cases collected on May 15. Flu virus PCR is negative. There were no bacteria cultured and identified from the healthy kids. Conclusion According to the results of epidemiological investigation, clinical symptoms and laboratory testing, the outbreak was caused by a-hemolytic streptococcus, therefore, the key control measures were to teach the pupils to wash their hands before meals and change new toothbrushes regularly. Morning exercise activity should be encouraged at school. Students with FUO should be identified, insolated and treated promptly in order to control the communicable disease from the very beginning. The students should only be permitted to come back school after total recovery.