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Molecular characterisation of type 1 polioviruses associated with epidemics in South Africa
C Chezzi1, N K Blackburn, B D Schoub
1Department of Virology, University of the Witwatersrand Medical School, Johannesburg, South Africa.
Abstract:
The molecular epidemiology of wild-type 1 polioviruses isolated in South Africa during 2 major poliomyelitis epidemics in the 1980s and during the pre- and inter-epidemic periods was investigated by partial sequence analysis across the VP1/2A junction. Poliovirus-specific primers were used to amplify and subsequently sequence the region of interest. Viruses belonging to different genotypes were found to have been responsible for the 2 outbreaks. The Gazankulu outbreak in 1982 was caused by a poliovirus genotype which was unique to South Africa and which circulated endemically throughout much of the country between 1980 and 1985. Two additional genotypes, imported from the Middle East and West Africa, cocirculated endemically with the South African genotype between 1982 and 1985. The 1988 epidemic in Kwazulu-Natal was attributed to an imported genotype apparently introduced into South Africa in 1985 from countries north of the border. This genotype displaced the 3 genotypes previously in circulation and continued to be transmitted within the country until 1989, when the last confirmed cases of poliomyelitis associated with wild-type viruses were documented. All circulating wild-type poliovirus strains appear to have been eliminated from South Africa.
Insights
Molecular epidemiology revealed distinct wild poliovirus genotypes caused South Africa's 1980s poliomyelitis epidemics. Imported and endemic strains circulated, with one genotype ultimately displacing others and leading to the documented elimination of wild poliovirus.
Area of Science:
- Molecular Epidemiology
- Virology
- Public Health
Background:
- Poliomyelitis epidemics occurred in South Africa during the 1980s.
- Understanding the genetic diversity and origins of circulating wild polioviruses is crucial for disease control.
Purpose of the Study:
- To investigate the molecular epidemiology of wild-type 1 polioviruses in South Africa.
- To determine the genotypes responsible for major poliomyelitis outbreaks and endemic circulation.
Main Methods:
- Partial sequence analysis of the VP1/2A junction of wild poliovirus isolates.
- Use of poliovirus-specific primers for amplification and sequencing.
Main Results:
- Two distinct poliomyelitis epidemics were driven by different poliovirus genotypes.
- A unique South African genotype circulated endemically from 1980-1985, alongside two imported genotypes.
- An imported genotype, introduced in 1985, displaced previous strains and was linked to the 1988 epidemic.
- Wild poliovirus transmission ceased in South Africa by 1989.
Conclusions:
- The study identified distinct endemic and imported wild poliovirus genotypes circulating in South Africa.
- Molecular analysis provided insights into the origins and displacement dynamics of poliovirus strains.
- Evidence suggests the successful elimination of wild poliovirus from South Africa.