Respiratory syncytial virus- and influenza virus-associated hospitalizations in infants less than 12 months of age.

Infants hospitalized because of respiratory syncytial virus (RSV) infection (n = 388) were significantly younger, had longer hospital stays, had a more severe course of disease, and required supplemental oxygen more often with longer duration of treatment as compared with those with influenza virus (n = 37) infection. Seasonal distribution varied, with RSV-associated hospitalizations peaking in January and influenza virus-associated hospitalizations in February. Congenital heart disease was more commonly a risk factor in infants with RSV infection.