title: Update: respiratory syncytial virus activity--United States, 1998-1999 season.
mesh_terms: D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D002648:Child; D002675:Child, Preschool; D004196:Disease Outbreaks; D005260:Female; D006801:Humans; D015994:Incidence; D007223:Infant; D008297:Male; D011159:Population Surveillance; D018357:Respiratory Syncytial Virus Infections / Q000175:diagnosis / Q000453:epidemiology*; D018570:Risk Assessment; D014481:United States / Q000453:epidemiology