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Outbreak of paralytic poliomyelitis in Namibia
A B van Niekerk1, J B Vries, J Baard
1National Institute for Virology, Johannesburg, South Africa.
Lancet (London, England)
|September 3, 1994
Summary
A 1993-1994 polio outbreak in Namibia occurred despite high oral poliovaccine (OPV) coverage. This highlights the need for enhanced acute flaccid paralysis (AFP) surveillance to detect susceptible populations and prevent future epidemics.
Area of Science:
- Epidemiology
- Virology
- Public Health
Background:
- The last confirmed poliomyelitis case in Namibia was in 1988.
- An outbreak of 27 paralytic poliomyelitis cases occurred between November 1993 and January 1994.
- The outbreak was concentrated in the southern health region, where infant oral poliovaccine (OPV) coverage was at least 80%.
Purpose of the Study:
- To investigate the factors contributing to a poliomyelitis outbreak in Namibia.
- To analyze the clinical presentation and vaccine status of affected individuals.
- To understand the genetic relationship of the outbreak poliovirus isolates.
Main Methods:
- Case ascertainment and clinical data collection for paralytic poliomyelitis.
- Analysis of patient age and oral poliovaccine (OPV) immunization status.
- Genotypic analysis of poliovirus isolates from the outbreak.
- Review of potential contributing factors such as sanitation and water supply.
Main Results:
- The outbreak predominantly affected children under 5 years old, with acute flaccid paralysis (AFP) as the main symptom.
- A significant proportion of affected individuals had received multiple doses of OPV, indicating vaccine failure or other contributing factors.
- Genotypic analysis revealed homology between outbreak isolates and earlier Namibian and West African strains.
- Factors such as urbanization, poor sanitation, inadequate water supply, and potential endemicity in neighboring areas were implicated.
Conclusions:
- Poliomyelitis epidemics can occur even in areas with high vaccine coverage.
- Improved acute flaccid paralysis (AFP) surveillance is crucial for early detection of outbreaks.
- Accurate estimation of vaccine coverage and identification of susceptible populations are essential for outbreak prevention strategies.