Invasive pneumococcal disease in Dallas County, Texas: results from population-based surveillance in 1995.

We studied the epidemiology of invasive disease caused by Streptococcus pneumoniae in 1995 among 1.9 million residents of Dallas County, Texas. The sociodemographic characteristics and chronic medical conditions of 432 patients were identified through active, population-based surveillance and review of medical records. The incidence of disease was 22 cases per 100,000 person-years and was highest for children < 2 years of age (136 cases per 100,000 person-years) and for adults > or = 65 years of age (80 cases per 100,000 person-years). Twenty percent of isolates were nonsusceptible to penicillin; the highest rates of resistance were among the youngest and oldest age groups (28% and 22% of isolates, respectively). An increased incidence of disease was associated with low income (42 cases per 100,000 person-years) and black race (39 cases per 100,000 person-years). The frequency of most chronic medical conditions increased with age; smoking, heavy alcohol use, and infection due to human immunodeficiency virus were most common between 30 and 64 years of age. Of otherwise healthy patients 30-64 years of age, 47% were current smokers, an association requiring further investigation. Characterizing groups at risk for invasive pneumococcal disease could aid in the development of prevention programs and increase the benefits from wide use of effective vaccines.