Abstract

2][3] Despite the secular trend for decreasing hospitalization rates overall, the number and rate of hospitalizations for persons with acute lower respiratory tract infections increasedsteadilyduringthelast20years.Almost 1.5 million persons were hospitalized in 1995 after an average increase of more than 28 000 per year since 1980. 1 The hospitalization rate for persons 65 years of age or older with pneumonia increased by 50% from 1985 to 1995. 3 The rates of acute lower respiratory tract infections cited above do not include exacerbations of asthma or chronic obstructive pulmonary disease (COPD).During the same period, the death rate for women with COPD doubled and the hospitalizationrateforpoorblackchildrenwith asthma was 4 times greater than that for children from middle-income families.8][9] These studies showed that influenza virus and respiratory syncytial virus (RSV) were frequently associated with lower respiratory tract illnesses resulting in hospitalization.Recognizing that these conditions are preventableor potentially preventable-with existing technology, this study was designed to examine comprehensively within a defined population the role of respiratory virus infections in acute respiratory conditions leading to hospitalization of persons of all ages with chronic underlying conditions. METHODS Clinical and Epidemiologic MethodsFor a 4-year period, July 1991 through June 1995, patients from 4 large clinics were enrolled within 1 day of ad-mission to the hospital.The participating clinics were the Casa de Amigos and Martin Luther King Clinics of the Harris County Hospital District (HCHD) and the Pasadena and West Clinics of Kelsey-Seybold Clinics, all located in