unless the perpetrators reveal themselves. An analysis of the distribution and number of reported cases will provide important clues regarding the source of infection and can be used both to guide law enforcement and to help all physicians in the community make a rapid and accurate diagnosis of new cases and begin optimal treatment without delay. A very large and efficient attack may truncate the dispersion of cases in space and time (even in this case, victims will not be affected immediately, as they would be with chemical agents), making effective intervention difficult even as it makes it more obvious that the cause is a deliberate release. Rapid and accurate epidemiologic investigation will nevertheless be a key factor in minimizing suffering and loss of life in bioterrorist incidents. Surveillance systems for collecting reports of such cases and appropriately trained staff to monitor for disease outbreaks are the foundation of public health epidemiology. Yet over the last few decades there has been severe erosion in the capacity of public health departments to conduct disease surveillance and epidemiologic investigation.
A rapid evaluation by public health epidemiologists is absolutely critical. Delays in determining the scope and magnitude of the exposure may result in illness and deaths that might have been avoided if a rapid response, based on accurate and timely surveillance data, was made.
Surveillance systems can be passive or active. The large majority of surveillance systems in place at local, state, and federal levels is passive. These rely on systems of disease reporting from health providers and are notorious for their poor sensitivity, lack of timeliness, and minimal coverage. They are inexpensive to implement, but the quality of information is greatly limited, and most are not well suited to the needs of modern disease surveillance, including that needed in the case of a biologic terrorist event. The single exception appears to be electronic laboratory reporting (described below), which can give useful and timely data for epidemiologic purposes.
The Centers for Disease Control and Prevention (CDC) oversees a large number of passive infectious disease surveillance systems. These systems are based on voluntary collaboration with state and local health departments, which in turn depend on physician-initiated reports of specific diseases or information from state health laboratories regarding bacterial or viral isolates. The best known system is the National Notifiable Disease Surveillance System, which the CDC describes as the backbone of collaborative reporting procedures involving clinicians, state, and local health departments, and the CDC. Clinicians, hospitals, and laboratories