According to The World Health Organization [WHO], Sickle-cell anaemia is particularly common among people whose ancestors come from sub-Saharan Africa, India, Saudi Arabia and Mediterranean countries. Migration raised the frequency of the gene in the American continent. In some areas of sub-Saharan Africa, up to 2% of all children are born with the condition. In broad terms, the prevalence of the sickle-cell trait (healthy carriers who have inherited the mutant gene from only one parent) ranges between 10% and 40% across equatorial Africa and decreases to between 1% and 2% on the north African coast and <1% in South Africa. This distribution reflects the fact that sickle-cell trait confers a survival advantage against malaria and that selection pressure due to malaria has resulted in high frequencies of the mutant gene especially in areas of high malarial transmission.

 

In west African countries such as Ghana and Nigeria, the frequency of the trait is 15% to 30%, whereas in Uganda it shows marked tribal variations, reaching 45% among the Baamba tribe in the west of the country. In Nigeria, by far the most populous country in the sub-region, 24% of the population are carriers of the mutant gene and the prevalence of sickle-cell anaemia is about 20 per 1000 births. This

means that in Nigeria alone, with a current population of over 208 million, 24% or approximately 50,000,000 carry the sickle cell trait. Currently, about 150,000 children are born annually in Nigeria with sickle-cell anemia.

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*Source: The World Health Organization [WHO]
http://apps.who.int/gb/archive/pdf_files/WHA59/A59_9-en.pdf

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