Although the importance of respiratory syncytial virus (RSV) as a respiratory pathogen in children is well recognised, more needs to be known about the overall disease burden it causes. A study at three US sites (Rochester (NY), Nashville and Cincinnati) has provided epidemiological data (Caroline Breese Hall and colleagues. New England Journal of Medicine 2009;360:588–98). Overall, 5067 children aged <5 years with acute respiratory infection (ARI) entered the study during the winter months (November–April) between 2000 and 2004. Of these, 919 …