Peroral infectivity trials had been done with human volunteers (Gary et al. 1987; Grohmann et al. 1981; Schiff et al. 1984 ), but we felt that they included too many uncontrolled variables. With support (1975) (1976) (1977) (1978) from the US EPA, we undertook peroral infectivity studies using young swine as experimental subjects. The Abstract of the final report to EPA (Cliver 1980) says: