Experimental infection of human volunteers with a swine influenzavirus antigenically related to the human A-Hong Kong-68 virus.

An influenzavirus of swine origin (swine/Taiwan/7310/70) antigenically closely related to the human A/Hong Kong/68 virus readily infected human volunteers. Those infected developed antihaemagglutinin and antineuraminidase antibodies to the human A/Hong Kong/68 virus as well as to the swine/Taiwan virus. The clinical reactions produced by the swine/Taiwan virus were, however, milder than those produced in volunteers infected with A/Hong Kong/68. In contrast, two other "classical" swine viruses (strains antigenically related to the prototype swine/Iowa/15/30 strain), immunologically distinct from the Hong Kong/68 virus, possessed low infectivity for man.