Impact of respiratory virus infections on persons with chronic underlying conditions

Context While hospitalization rates have declined overall, hospitalizations for acute lower respiratory tract infections have increased steadily since 1980. Development of new approaches for prevention of acute respiratory tr act conditions requires studies of the etiologies of infections and quantif ication of the risk of hospitalization for vulnerable patients. Objective To determine the frequency of specific virus infections associate d with acute respiratory tract conditions leading to hospitalization of chr onically ill patients. Design Analysis of viral etiology of patients hospitalized with acute respi ratory tract conditions between July 1991 and June 1995. Setting Four large clinics and related hospitals serving diverse population s representative of Harris County, Texas. Patients A total of 1029 patients who were hospitalized for pneumonia, trac heobronchitis, bronchiolitis, croup, exacerbations of asthma or chronic obs tructive pulmonary disease, and/or congestive heart failure. Main Outcome Measure Virus infection, defined by culture, antigen detection , and significant rise in serum antibodies, by underlying condition; hospit alization rates by low- vs middle-income status. Results Ninety-three percent of patients older than 5 years had a chronic u nderlying condition; a chronic pulmonary condition was most common. Patient s with chronic pulmonary disease from low-income populations were hospitali zed at a rate of 398.6 per 10 000, almost 8 times higher than the rate for patients from middle-income groups (52.2 per 10 000; P<.001). Of the 403 pa tients (44.4% of adults and 32.3% of children) who submitted convalescent s erum specimens for antibody testing, respiratory tract virus infections wer e detected in 181 (44.9%). influenza, parainfluenza, and respiratory syncyt ial virus (RSV) infections accounted for 75% of all virus infections. Conclusions Our study suggests that respiratory virus infections commonly t rigger serious acute respiratory conditions that result in hospitalization of patients with chronic underlying conditions, highlighting the need for d evelopment of effective vaccines for these viruses, especially for parainfl uenza and RSV.