A look at the facts surrounding the outbreak to determine if anything seems unusual or indicative of bioterrorism should suffice. Since a disease outbreak can be the result of intentional contamination, the differential diagnosis of an outbreak should first be considered. The possibilities include a spontaneous outbreak of a known endemic disease, a spontaneous outbreak of a new or reemerging disease, a laboratory accident, or an intentional attack with a biological agent. Epidemiologic tools can assist in differentiating between these possibilities. The cause of a disease or even the occurrence of something unusual may be very difficult to determine, especially if the initial cases are few.
Surveillance needs to be more than routine.
Not only unusually high rates of illness but also unusual diseases should signal a warning. For example, even one case of inhalation anthrax should cause immediate concern and action. Unlike chemical terrorism, biological terrorism is not immediately obvious but may appear insidiously, with primary-care providers witnessing the first cases. However, it may not even be emergency room personnel who first detect a problem. All epidemiologic data should be tracked and aggressively followed to ensure the most rapid recognition and response.