The spores of B. anthracis are extremely stable and may remain viable for many years in soil and water from which they are ingested and cause disease in animals. In the event of a bioterrorist attack, inhalational disease would be the most likely presentation after exposure to aerosolized anthrax spores. The incubation period is usually 1 to 6 days, but can be as long as 60 days. Initial symptoms of fever, malaise, fatigue, cough and mild chest discomfort are followed in 24 to 72 hours by severe respiratory distress with dyspnea, diaphoresis, stridor and cyanosis. Shock and death occur within 24 to 36 hours after the onset of severe symptoms secondary to hemorrhagic mediastinitis and overwhelming sepsis.
Physical findings are non-specific for diagnosis.
A widened mediastinum may be seen on chest X-ray and is an important diagnostic clue, however pulmonary infiltrates are not seen. The bacterium is detectable by Gram stain of the blood and by blood culture late in the course of illness. Microbiologists need to be alert to the possibility that a gram-positive rod in the blood may not represent a contaminant as is typically the case. Nearly all inhalation anthrax cases in which treatment was begun after patients were significantly symptomatic have been fatal, regardless of treatment. Supportive therapy for shock, fluid volume deficit and adequacy of airway may all be needed.