Pulmonary function changes in children after respiratory syncytial virus infection in infancy.

During the last 20 years, an association between respiratory syncytial virus (RSV) bronchiolitis or pneumonia in infants and abnormal pulmonary function later in childhood has been established. Study designs have varied considerably, but most investigators have used an observational approach in which children with early bronchiolitis or pneumonia are identified and pulmonary function is measured later in childhood. Decreased forced expiratory flows at mid-lung volumes and increased airway reactivity have been demonstrated consistently in most studies. Few studies, however, have addressed the issue of whether the early symptomatic RSV infection caused the subsequent abnormalities in pulmonary function. An atopic tendency does not appear to explain the underlying association between early RSV infection and subsequent abnormal pulmonary function. Evidence suggests that infants with symptomatic bronchiolitis have an underlying deficit in pulmonary function that might contribute to the abnormalities documented later in childhood. The issue of causation could be addressed by intervention studies in which RSV is prevented or treated and differences in pulmonary function are observed. Several small prospective studies of children enrolled in early controlled trials of ribavirin treatment of RSV lower respiratory tract infection have not consistently demonstrated differences between infants in treated and control groups. Larger studies of the effect of ribavirin treatment, immunoglobulin prophylaxis, or immunization (when it becomes available) on subsequent pulmonary function and airway hyperreactivity may resolve this important issue.