Lesson 2 of 5
In Progress

Epidemiology, Risk Factors, and Etiology


CAP is the second most common cause of hospitalization and the most common infectious cause of death. Approximately 650 adults are hospitalization with CAP every year per 100,000 of population. This accounts to 1.5 million unique CAP hospitalizations each year.

For patients with age ≥ 65 years old, the annual incidence of hospitalization for CAP is approximately 2000 per 100,000 in the United States. This indicates that 2% of the older adult population will be hospitalized for CAP annually.

CAP is associated with increased long-term mortality. With mortality rates at 6.5% during hospitalization, 13% 30 days after hospitalization, 23% 6 months after hospitalization, and 31% a year after hospitalization.

Risk Factors

* Other lifestyle factors – including crowded living conditions (eg. Prisons, homeless shelters), residence in low-income settings, and exposure to environmental toxins (eg. Solvents, paints, or gas)

A combination of these risk factors in patients is additives in terms of potential risk for CAP.


The causative pathogen in CAP in adult patients is most commonly viral, with human rhinovirus and influenza most common. However, in a large proportion of cases (up to 62%), no pathogen is detected despite extensive microbiologic evaluation.