The worldwide eradication of poliomyelitis

Poliomyelitis, an infectious disease with acute and persistent flaccid para lysis is caused by poliovirus (types 1, 2 or 3), an enterovirus. The infect ion is asymptomatic in 95% of infected subjects. Most of the paralytic case s occur in adolescents or adults in the course of polio type 1 infection. In the prevaccination era, in countries with poor hygienic conditions, infe ction in early childhood was common, mostly asymptomatic, and immunity in t he population prevailed. In developed countries polio often struck adolesce nts and adults taking its toll in paralytic disease. The introduction of va ccination with the Salk vaccine (I PV Inactivated Polio Vaccine) in the USA and in Europe in 1956 and with the Oral Polio Vaccine (OPV) developed by S abin worldwide in the early sixties made it possible to control the epidemi c in large geographic areas, but it could not eliminate the disease worldwi de. Poliomyelitis is still endemic in Central Africa and in the Indian subc ontinent. Acts of war led to the reduction in the vaccination rate in different geogr aphic areas, and smaller epidemics with wild virus but also with reverted v accine strains occurred. In some parts of the world the rate of vaccination also declined due to elimination of poliomyelitis, and it came to small ep idemics of paralytic polio mainly caused by reverted vaccine strains circul ating in the population. Reverted vaccine strains also remain a central problem in the eradication o f poliomyelitis projected for 2005 by the World Health Organisation. A high vaccination rate, preferably with 3 doses of OPV in infancy or early child hood, and exact worldwide monitoring of cases is indispensable for the erad ication. For the complete eradication of poliovirus the live vaccine OPV would have to be changed to an inactivated vaccine IPV worldwide. However, this is pre sently unachievable, because of logistic problems and high costs.