Surveillance methods that can detect disease at an earlier stage are an important research direction for public health surveillance. These methods are generally referred to as syndromic surveillance because they have the goal of recognition of outbreaks based on the symptoms and signs of infection and even its effects on human behavior prior to first contact with the health care system. 8 Because the data used by syndromic surveillance systems cannot be used to establish a specific diagnosis in any particular individual, syndromic surveillance systems must be designed to detect signature patterns of disease in a population to achieve sufficient specificity. For example, it would be absurd to use only the symptom of fever to attempt to establish a working diagnosis of inhalational anthrax in an individual, but it would be very reasonable to establish a working diagnosis of anthrax release in a community if we were to observe a pattern of 1,000 individuals with fever distributed in a linear streak across an urban region consistent with the prevailing wind direction two days earlier. It would be beyond reasonable and, in fact, imperative to establish a working diagnosis of public health emergency if presented with such information.