Pneumonias can be roughly differentiated by symptoms
• “Typical pneumonia” - patient usually very ill
• Fever, cough productive of purulent (pus – yellow or green) and/or rusty sputum (red blood cells), dyspnea, pleuritic pain, lobar pattern of consolidation by x-ray
• S. pneumoniae, H. influenzae, M. catarrhalis

• “Atypical pneumonia” - illness may be mild
• "Walking pneumonia"
• Fever, dry (non-productive) cough, interstitial pattern of fibronodular or patchy infiltrates by x-ray (may be a surprise to physician!)
• Sputum (if present) scanty, thin or white
• Less likely to have pleuritic pain or pleural effusion
• M. pneumoniae, C. pneumoniae, Legionella sp., viruses