INCIDENCE OF COMMUNITY-ACQUIRED PNEUMONIA REQUIRING HOSPITALIZATION -RESULTS OF A POPULATION-BASED ACTIVE SURVEILLANCE STUDY IN OHIO

Background: Pneumonia is the leading cause of death due to infectious diseases in the United States; however, the incidence of most infectio ns causing community-acquired pneumonia in adults is not well defined. Methods: We evaluated all adults, residing in 2 counties in Ohio, who were hospitalized in 1991 because of community-acquired pneumonia. In formation about risk factors, symptoms, and outcome was collected thro ugh interview and medical chart review. Serum samples were collected f rom consenting individuals during the acute and convalescent phases, a nd specific etiologic diagnoses were assigned based on results of bact eriologic and immunologic tests. Results: The incidence of community-a cquired pneumonia requiring hospitalization in the study counties in 1 991 was 266.8 per 100 000 population; the overall case-fatality rate w as 8.8%. Pneumonia incidence was higher among blacks than whites (337. 7/100 000 vs 253.9/100 000; P<.001), was higher among males than femal es (291.4 vs 244.8; P<.001), and increased with age (91.6/100 000 for persons aged <45 years, 277.2/100 000 for persons aged 45-64 years, an d 1012.3/100 000 for persons aged greater than or equal to 65 years; P <.001). Extrapolation from study incidence data showed the projected a nnual number of cases of community-acquired pneumonia requiring hospit alization in the United States to be 485 000. These data provide previ ously unavailable estimates of the annual number of cases that are due to Legionella species (8000-18 000), Mycoplasma pneumoniae (18 700-10 8 000), and Chlamydia pneumoniae (5890-49 700). Conclusions: These dat a provide information about the importance of community-acquired pneum onia and the relative and overall impact of specific causes of pneumon ia. The study provides a basis for choosing optimal empiric pneumonia therapy, and allows interventions for prevention of pneumonia to be ta rgeted at groups at greatest risk for serious illness and death.