OutbreakInvestigation概述.ppt

* * * On Dec.3rd, 2004, the national emergency surveillance system reported 142 suspected cases of paratyphoid fever in a rural boarding school located in Lingchuan county, Guangxi province. * Does the observed number exceed the expected number观察到的数量超过了预计的数量了吗 Compare current numbers with numbers from comparable previous times将目前的数量与以前可比的数量进行对比 Are there any factors that may have led to increased reporting存在可能导致增大报告的任何因素吗 Is it worthwhile to investigate? 值得花时间或精力调查吗？ * 411 cases met the case definition. The main signs and symptoms reflected systemic illness. 69% of cases had a high fever, 55% a dry throat and 21% a nonproductive cough. These were usual symptoms of paratyphoid fever. * Salmonella enterica serovar paratyphi A was identified in 24% of the 173 blood specimens and 7% of the 61 stool specimens examined. * In this diagram the Black triangles represent the true cases of the disease in which we are interested. The orange dots represent other diseases or conditions that could be confused with our disease of Interest. A good case definition will separate our disease of interest from other diseases or conditions. However, we rarely or never get a perfect case definition that completely segregates true cases from non-cases. One way to handle this is to divide the range into different levels. Each level has additional restrictive criteria used in the case definition. Thus each level will exclude more and more of the other conditions and include less and less of the real cases. * Our case definition was any boarding school student or employee having onset of fever (≥37.5°C), and headache, dry throat, nonproductive cough or diarrhea, between Nov. 9—Dec.25, 2004. * * To search for cases, we reviewed clinical records in the school clinic, village clinic, and township hospital. We also reviewed the daily temperature readings, signs, and symptoms of students and employees, all of whom had been examined by school doctors, and discussed potential risk fact