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

During the last 20 years, an association between respiratory syncytial viru s (RSV) bronchiolitis or pneumonia in infants and abnormal pulmonary functi on later in childhood has been established. Study designs have varied consi derably, but most investigators have used an observational approach in whic h children with early bronchiolitis or pneumonia are identified and pulmona ry function is measured later in childhood. Decreased forced expiratory flo ws at mid-lung volumes and increased airway reactivity have been demonstrat ed consistently in most studies. Few studies, however, have addressed the i ssue of whether the early symptomatic RSV infection caused the subsequent a bnormalities in pulmonary: function. An atopic tendency does not appear to explain the underlying association between early RSV infection and subseque nt abnormal pulmonary function. Evidence suggests that infants with symptom atic bronchiolitis have an underlying deficit in pulmonary function that mi ght contribute to the abnormalities documented later in childhood. The issu e of causation could be addressed by intervention studies in which RSV is p revented or treated and differences in pulmonary function are observed. Sev eral small prospective studies of children enrolled in early controlled tri als of ribavirin treatment of RSV lower respiratory tract infection have no t consistently demonstrated differences between infants in treated and cont rol groups. Larger studies of the effect of ribavirin treatment, immunoglob ulin prophylaxis, or immunization (when it becomes available) on subsequent pulmonary function and airway hyperreactivity may resolve this important i ssue.