CAP affects >5 million adults each year in the United States, 80% of whom are treated on an outpatient basis. CAP causes >55,000 deaths annually and is associated with an overall yearly cost of ~$12 billion.

• Incidence rates of CAP are highest at the extremes of age (i.e., <4 and >60 years).
• Risk factors for CAP include alcoholism, asthma, immunosuppression, institutionalization, and an age of ≥70 years (vs. 60-69 years).
• Many factors—e.g., tobacco smoking, chronic obstructive pulmonary disease, colonization with methicillin-resistant S. aureus (MRSA), recent hospitalization or antibiotic therapy—influence the types of pathogens that should be considered in the etiologic diagnosis.