Antigenic and Genetic Analysis of A/Hong Kong (H3N2) Influenza Viruses Isolated from Swine and Man

Two H3N2 strains of influenza A virus isolated from pigs in Japan and Thailand were characterized antigenically and genetically. A/swine/Wadayama/5/69 (isolated in Japan in 1969) was antigenically similar to a human strain, A/Aichi/2/68, while A/swine/Bangkok/9/78 (a swine isolate in Thailand) was closely related to A/Bangkok/36/78, a contemporary human isolate. Gel electrophoresis and oligonucleotide mapping of the virus RNA revealed genetic similarity between A/swine/Wadayama/5/69 and A/Aichi/2/68, and between A/swine/Bangkok/9/78 and A/Bangkok/36/78, suggesting the derivation of swine H3N2 strains from contemporary human strains.