The higher frequency in the sub Saharan Africa is thought to be due to the selective advantage the gene confers on the traits (heterozygotes state) in malaria zone. Nigeria is the most populous country in this region with about 24% frequency of the mutant gene. The prevalence of sickle cell anaemia in Nigeria is about 20 per 1000 life births. This implies that Nigeria may have the highest burden of the disease in the world.