Rationale: Legionella is associated with high fever, diarrhea, confusion, and headache, and Mycoplasma and Chlamydophila usually have a more indolent course. Viral pneumonias often present with typical symptoms of upper respiratory infection. C. psittaci, Coxiella, and Legionella usually have a specific history of exposure (e.g., birds, pigs, or environmental). Truly purulent sputum, as is seen in S. pneumoniae (a major cause of typical pneumonia) is uncommon with other listed pathogens.