1931

Richard Shope (Rockefeller Institute at Princeton, raised on Iowa farms, discovers swine flu (traced to Cedar Rapids Swine Show in October 1918 and returning annually with onset of winter), and its close antigenic relationship to human influenza virus. In 1934, Thomas Francis (Michigan) isolated Type A influenza virus by discovering antibodies in bloodstream of animals that convalesced from influenza infection; Shope, also in 1934, found that swine flu antibodies could protect ferrets and mice against human influenza and vice versa, though human and swine viruses were not identical (Kolata, 77). Drawing blood in 1934 from survivors of 1918 epidemic, Shope and British scientists Smith, Andrewes, and Laidlaw found that people who had survived the 1918 flu had antibodies that completely blocked Shope’s swine flu virus. People who were born after 1918 did not have those antibodies . . . They were the antibodies left behind in the flu’s survivors and they showed that the human flu virus was, in fact, one and the same as the swine flu. The 1918 influenza virus, it seemed, may have survived after all, in the bodies of the pigs. . . .There was a swine flu connection – probably people had given the flue to pigs, scientists proposed, and the virus may have remained in pigs, lying dormant until, one day, it might strike back at people. . . .The 1918 epidemic came in two waves, a mild flue in the spring of 1918 followed by the killer flue in the fall. And it seemed that the two flu strains were closely related. Infections with the first strain protected against the second.” (78-81). In 1941, Francis isolated Type B influenza virus (Galambos & Sewell, 45-46).