The workup of a febrile patient who presents with an influenza-like illness in the setting of a national or regional anthrax outbreak presents a unique challenge to the physicians who initially evaluate this patient, and the diagnostic challenge can be even more profound during the influenza season. Based on information gathered from the recent inhalational anthrax cases, we have developed an algorithm to be used by physicians in the emergency department to evaluate patients with influenza-like illnesses during a national or regional anthrax outbreak. The algorithm necessitates stays no longer than 24 hours in the emergency department or hospital.