Have we had Hong Kong flu before?
D000367:Age Factors; D000368:Aged; D000906:Antibodies / Q000032:analysis*; D004196:Disease Outbreaks; D006801:Humans; D007251:Influenza, Human / Q000276:immunology*; D008875:Middle Aged; D009975:Orthomyxoviridae / Q000276:immunology*
D000906:Antibodies