摘要：Objectives. This study investigated retrospective validation of a prospective surveillance system for unexplained illness and death due to possibly infectious causes. Methods. A computerized search of hospital discharge data identified patients with potential unexplained illness and death due to possibly infectious causes. Medical records for such patients were reviewed for satisfaction of study criteria. Cases identified retrospectively were combined with prospectively identified cases to form a reference population against which sensitivity could be measured. Results. Retrospective validation was 41% sensitive, whereas prospective surveillance was 73% sensitive. The annual incidence of unexplained illness and death due to possibly infectious causes during 1995 and 1996 in the study county was conservatively estimated to range from 2.7 to 6.2 per 100 000 residents aged 1 to 49 years. Conclusions. Active prospective surveillance for unexplained illness and death due to possibly infectious causes is more sensitive than retrospective surveillance conducted through a published list of indicator codes. However, retrospective surveillance can be a feasible and much less labor-intensive alternative to active prospective surveillance when the latter is not possible or desired. Globalization of food supply, intracontinental and intercontinental travel, climactic changes, and overcrowding, among other factors, have increased the mobility of microbial agents and thereby the risk of infectious diseases posed to humans. Outbreaks of Ebola hemorrhagic fever in Zaire and bubonic plague in India during the early 1990s are reminders that emerging and reemerging infectious diseases remain a threat to the health and well-being of the global community. 1 – 3 As demonstrated by the emergence of West Nile viral encephalitis, hantavirus pulmonary syndrome, and AIDS, the United States is not impervious to emerging epidemics. 4 , 5 The agents that cause AIDS, Lyme disease, Legionnaires' disease, toxic shock syndrome, and hepatitis C were identified only after the occurrence of significant morbidity or mortality. 6 Reliance on traditional responsive methods to identify infectious agents may delay prevention and control efforts. While advancements in biomedical technology have allowed for more rapid identification of microbial agents, population-based surveillance networks capable of identifying trends in infectious disease symptomatology have deteriorated. 7 Systematic prospective study of the epidemiology of infectious disease syndromes is needed for earlier detection of and response to emerging infections. 6 , 8
