This is a prospective, pilot study that will noninvasively measure feNO in children 0-4 years of age admitted to Winthrop University Hospital, as well as controls (children in the same age range without respiratory conditions and who are well enough to perform the test). Hospitalized children will be tested for RSV (enzyme immunoassay (EIA) & DFA) and via direct fluorescent antigen technique (DFA) for influenza A & B, parainfluenza, human metapneumovirus and adenovirus.