Respiratory syncytial virus.
D002648:Child; D002675:Child, Preschool; D003428:Cross Infection / Q000453:epidemiology / Q000209:etiology*; D006801:Humans; D007223:Infant; D012136:Respiratory Syncytial Viruses / Q000472:pathogenicity; D012141:Respiratory Tract Infections / Q000453:epidemiology / Q000209:etiology*; D010253:Respirovirus Infections / Q000175:diagnosis* / Q000453:epidemiology; D014481:United States