Pneumococcal pneumonia: epidemiology and clinical features.

Pneumoccal pneumonia is a common illness; the highest incidence occurs at the extremes of age. The rate of pneumococcal bacteremic pneumonia is higher in blacks than in whites and 41 times higher in those with human immunodeficiency virus (HIV) infection than in individuals of the same age who are not HIV infected. Risk factors for pneumococcal pneumonia include dementia, seizure disorders, cigarette smoking, congestive heart failure, cerebrovascular disease, institutionalization, and chronic obstructive pulmonary disease. Outbreaks of pneumococcal pneumonia occur in situations of overcrowding such as in jails or in shelters for the homeless. Streptococcus pneumoniae is the most common cause of community acquired pneumonia requiring hospitalization, accounting for up to 50% of all such cases. The mortality rate from this infection varies considerably in reported studies ranging from 7% to 36%. Bacteremic pneumococcal pneumonia often has a complicated course. Respiratory failure, meningitis, pleural effusion, and empyema are the most common complications. The radiographic manifestations of pneumococcal pneumonia vary, but in general lobar consolidation is more likely to be associated with bacteremia. Cavitation is unusual.