Poliomyelitis in developing countries: lower limb paralysis and injections.

The distribution of muscle paralysis due to poliomyelitis is different in temperate and tropical countries. In temperate countries, 49% of children with paralysis were affected only in the legs compared with 85% in developing countries, 79% and 89% respectively had affected legs with other paralysis. This suggests that correction for lameness surveys is unnecessary. Muscles frequently injected and those with adjacent motor neurone tracts in the central nervous system were much more frequently affected in Nigerian than in UK children, whereas paralysis in other muscles was less frequent than in the UK children. This and other evidence points to a major causal role for injections in the high prevalence of polio in developing countries. Proof may however be impossible to obtain because less than 0.5% of all injections are followed by paralysis. There may also be damage to motor neurones, without paralysis, which may lead to later disabilities. Injections should be given to young children only when absolutely necessary.