THIS EXHIBIT presents evidence that in clinical poliomyelitis a systemic phase, which may be accompanied by symptoms of the minor illness or may be entirely asymptomatic, precedes involvement of the central nervous system. Only recently has it become apparent that, during the systemic infection, virus is present in the blood stream for several days. Chimpanzees and cynomolgus monkeys experimentally infected by a natural route, i. e., orally, have been shown to have viremia between the third and eighth days after virus ingestion. In the case of the cynomolgus monkey, this is during the incubation period, some days before the onset of paralysis. In experimental animals, viremia is followed by prompt and early appearance of antibodies, which have been found at the time of onset of signs of disease.
—The spread of poliomyelitis through a community is better understood when it is realized that the majority of infections are