title: Flu hits young and middle-age adults.
mesh_terms: D000328:Adult; D017677:Age Distribution; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype / Q000302:isolation & purification*; D007252:Influenza Vaccines; D007251:Influenza, Human / Q000453:epidemiology* / Q000517:prevention & control*; D008875:Middle Aged; D009017:Morbidity; D014481:United States; D055815:Young Adult
chemical_list: D007252:Influenza Vaccines