Death of motor neurones following invasion of the central nervous system by poliovirus may result in paralysis of specific muscles. Virulence may be tested by injection into monkeys by routes which bypass natural infection. Transmissibility is also very important, but cannot be measured, only inferred. An infection may lead to immunity or paralysis. In epidemics, the highest incidence among children 0-2 years was 2% and among those over 10 years was 25%: these figures fit a model of genetic susceptibility of (...) homozygotes and heterozygotes with phenotypic susceptibility increasing with age. Hypogamma-globulinemics, some neonates and pregnant women are more susceptible than others. Intra-muscular injections may increase the risk of paralysis. Strenuous exercise and IM injections given when poliovirus has already reached the spinal cord can increase the severity of paralysis or convert a non-paralytic attack to paralysis. Although vaccines reduced polio in temperate countries, polio was thought to be no problem in the tropics. Since 1977 polio has been recognised as a massive problem in the third world: because it affects babies and very young children, it is properly infantile paralysis. (shrink)

At the beginning of the twentieth century, poliomyelitis presented a scientific and medical challenge of a complexity similar to that of AIDS now. Research on polio, mainly in the US, gradually became focussed to solving basic questions, but was held up by the lack of suitable laboratory techniques. The financing of the research and the wide range of basic topics funded were the model for later medical science. The problem of polio, at least in the wealthier temperate countries, has been (...) solved by the use of vaccines. Many fundamental questions about the mechanism of the disease remained unsolved and this lack of knowledge has contributed to many unfortunate accidents. The history of polio has many lessons for AIDS researchers. (shrink)