Review of epidemiology and clinical risk factors for severe respiratory syncytial virus (RSV) infection.

Respiratory syncytial virus (RSV) infection is the most frequent reason for hospitalization of infants in developed countries. Premature birth without or, especially, with chronic lung disease of prematurity, congenital heart disease, and T-cell immunodeficiency are conditions that predispose to more severe forms of RSV infection. Incomplete development of the airway, damage to the airway, and airway hyperreactivity underlie the increased morbidity of RSV infection in prematurely born infants. Pulmonary hypertension and cyanosis are associated with worse outcomes in infants with congenital heart disease, and prolonged viral replication accounts for more severe illness in immunocompromised individuals.