Influenza surveillance.
D000293:Adolescent; D000328:Adult; D000914:Antibodies, Viral / Q000032:analysis; D002648:Child; D002675:Child, Preschool; D002681:China; D006801:Humans; D007251:Influenza, Human / Q000453:epidemiology*; D009975:Orthomyxoviridae / Q000276:immunology / Q000302:isolation & purification; D012621:Seasons
D000914:Antibodies, Viral