title: Subtype of influenza A isolates--United States.
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002675:Child, Preschool; D005260:Female; D006801:Humans; D009980:Influenza A virus / Q000145:classification; D007251:Influenza, Human / Q000382:microbiology*; D008875:Middle Aged; D014481:United States