If syndromic surveillance is the answer, what is the question?

THE EVENTS OF FALL 2001, particularly the mailing of anthrax spores to public officials and the consequent anthrax cases, have had a dramatic and immediate effect on the perception of public health in the United States on the part of policy makers, government officials, and the general public. A public health infrastructure that has generally been undervalued and underfunded for several decades has seen a sudden infusion of substantial federal funds appropriated by the U.S. Congress and distributed to state and local health departments by the U.S. Centers for Disease Control and Prevention (CDC). This infusion of federal funds comes just as most localities and states are facing mounting budget deficits and are being forced to reduce spending across the board, including spending on important health care delivery and public health programs. As a result, these new federal funds and the programs they support are having a disproportionate impact on the priorities and activities of local and state health departments. Those responsible for appropriating and disbursing these federal funds have almost invariably referred to the need to strengthen public health in general and to the desirability of improving our ability to detect and respond appropriately to both manmade and naturally occurring infectious disease threats. However, it seems inarguable that the impetus behind this federal largesse is to improve preparedness for possible future bioterrorist events, which some policy makers and technical experts with access to classified information believe are inevitable. Given the decades of underfunding of public health that preceded the events of Fall 2001, it is difficult to envision comparable levels of funding being made available for the sole purpose of enhancing our ability to detect, respond to, and study naturally occurring infectious diseases, even under the recently popular rubric of “emerging and re-emerging” infections. Among the activities being funded as a part of the efforts to improve our nation’s capacity to detect and respond rapidly to new infectious disease threats is syndromic surveillance. Syndromic surveillance is generally meant to refer to the monitoring of the frequency (e.g., the number or rate of episodes) of illnesses with a specified set of clinical features (e.g., fever and respiratory complaints, vesicular skin rashes, diarrhea, etc.) in a given population (e.g., members of a health maintenance organization, residents of a given geographic region, etc.), without regard to the specific diagnoses, if any, that are assigned to them by clinicians. Because many of the infectious agents considered likely to be used in a bioterrorist attack (e.g., smallpox, plague, anthrax, tularemia, and brucellosis, among others) initially produce nonspecific clinical manifestations (e.g., fever, malaise, cough, fatigue, anorexia, etc.), and because even the best-prepared clinicians may not suspect one of these illnesses in the absence of more specific findings, it seems plausible that careful monitoring of a syndrome like febrile respiratory illness can provide to public health officials the earliest evidence of such an attack. Earlier detection of a bioterrorist event would then enable more rapid targeting and implementation of effective control measures, including vaccination, chemoprophylaxis, or quarantine, and lead to a consequent reduction in morbidity and mortality. Various approaches are being used to amass the data needed to measure the number or rate of such illnesses in a population, including enhanced passive reporting of illnesses seen in health care settings (e.g., hospitals, emergency departments, and outpatient clinics); active case finding in similar settings; monitoring of 911 calls; and making use of data normally being entered into computerized data bases by health care providers such as health maintenance organizations for billing and other purposes. Attempts are even being made to monitor illnesses in the community irrespective of whether the ill individuals seek medical care by examining sales of over-the-counter medications and other items. While some of these approaches are labor intensive,