Bioterrorism agents that could cause outbreaks or clusters characterized by respiratory symptoms - differential diagnosis and key features

Agent	Time to onset	Chest radiograph	Fatality	Onset to respiratory failure
Anthrax (inhalation)	1 to 6 days	Mediastinal widening, pleural effusions	90 percent	1 to 3 days
Plague (pneumonic)	2 to 3 days	Bilateral infiltrates, may have pleural effusions	90 percent	Within 1 day
Tularemia	2 to 10 days	Bilateral infiltrates hilar adenopathy	30 percent without therapy, <5 percent with therapy	Low incidence
Legionella	2 to 10 days	Variable, bilateral subsegmental infiltrates or consolidation	15 percent	Variable incidence
Influenza	1 to 2 days	Variable bilateral interstitial or alveolar infiltrates	10 to 25 percent in those with underlying diseases	Variable incidence
Ricin (inhalation)	18 to 24 hours	Likely bilateral infiltrates/acute respiratory distress syndrome	High	Likely within 30 hours

Adapted from: Karwa M, Currie B, Kvetan V. Bioterrorism: Preparing for the impossible or the improbable. Crit Care Med 2005; 33:S75.

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