OUTBREAK OF PARALYTIC POLIOMYELITIS IN NAMIBIA

The last confirmed case of poliomyelitis in Namibia had been reported in 1988. However, between Nov 8, 1993, and Jan 7, 1994, 27 cases of paralytic poliomyelitis were confirmed in the country. The outbreak was limited to the south health region; at least 80% of infants in this region have received four doses of oral poliovaccine (OPV) by the age of 1 year. Acute flaccid paralysis (AFP) was the predominant clinical presentation during the outbreak. The patients' ages ranged from 13 months to 12 years; 24 were younger than 5 years. Of the 26 patients whose vaccine status was known, 14 had received four doses of OPV, 6 had one or two doses, and 6 no vaccine. Genotypic analysis showed 86% homology of outbreak isolates with a 1982 Namibian isolate and west African isolates. Factors that may have had a role in the outbreak include establishment of a pool of susceptible people, rapid urbanisation, inadequate sanitation, poor water supply, and possible endemicity of poliovirus in neighbouring areas. Epidemics can occur in areas of high vaccine coverage. Our findings emphasise the need to improve AFP surveillance activities and the estimation of vaccine coverage to identify areas of potential susceptibility for outbreaks.