Influenza in 1973.
D000914:Antibodies, Viral; D006385:Hemagglutination Inhibition Tests; D006801:Humans; D007251:Influenza, Human / Q000453:epidemiology / Q000382:microbiology; D009975:Orthomyxoviridae / Q000276:immunology*; D013019:South Africa
D000914:Antibodies, Viral