Syndromic surveillance and bioterrorism-related epidemics

Abstract

To facilitate rapid detection of a future bioterrorist attack, an increasing number of public health departments are investing in new surveillance systems that target the early manifestations of bioterrorism-related disease. Whether this approach is likely to detect an epidemic sooner than reporting by alert clinicians remains unknown. The detection of a bioterrorism-related epidemic will depend on population characteristics, availability and use of health services, the nature of an attack, epidemiologic features of individual diseases, surveillance methods, and the capacity of health departments to respond to alerts. Predicting how these factors will combine in a bioterrorism attack may be impossible. Nevertheless, understanding their likely effect on epidemic detection should help define the usefulness of syndromic surveillance and identify approaches to increasing the likelihood that clinicians recognize and report an epidemic.

Figure 1

Number of cases of syndromic illness by time in a hypothetical bioterrorism attack and two pathways to establishing a diagnosis: syndromic surveillance coupled with public health investigation (upper pathway) and clinical and diagnostic evaluation of patients with short-incubation period disease (lower pathway). A, scenario favoring earlier detection by means of clinical evaluation. B, scenario favoring earlier detection by means of syndromic surveillance.

Figure 2

Timeline to presumptive anthrax diagnosis, 11 patients with inhalational anthrax, 2001, United States. Abbreviations: Dx, diagnosis; OutPt, outpatient visit followed by discharge home; ER, emergency room visit followed by discharge home. *Diagnosis delayed—initial blood cultures were negative in three patients who received antibiotic therapy before culture specimens were collected, requiring use of special diagnostic tests. For patients 1–10, case numbers correspond to those in report by Jernigan et al. (13); patient 11 reported by Barakat et al. (14). A, timeline begins with presumed date of anthrax exposure, available for six patients. B, timeline begins with day of illness onset for five patients without recognized date of exposure.