Influenza.
D000328:Adult; D000368:Aged; D002648:Child; D003431:Cross-Cultural Comparison; D004196:Disease Outbreaks; D006801:Humans; D009980:Influenza A virus / Q000145:classification / Q000302:isolation & purification; D009981:Influenza B virus / Q000145:classification / Q000302:isolation & purification; D007251:Influenza, Human / Q000453:epidemiology* / Q000821:virology