One unforseen challenge has been the advent of HIV/Aids, which has thrived amid the poverty. Although sub-Saharan Africa is home to 10% of the world's population, it now accounts for some two-thirds of all those living with HIV. Rates of infection vary widely. As a result, life expectancy has fallen below 40 years in nine countries - worst affected being Zambia (32.7 years) and Zimbabwe (33.9 years) - according to UN data.
Recent projections suggest that if more is not done to stem the epidemic, 89 million more Africans could be affected in the next two decades - up to 10% of the population.
The majority of those who fall victim to HIV/Aids are adults in their prime, the most productive members of society. Millions of children have lost one or both parents. Often it falls to older siblings or surviving grandparents to care for the family left behind.
Signs of a drop in HIV infection levels have been spotted in some East African states - notably Uganda, where prevalence nationally fell from 13% in the early 1990s to 4.1% by the end of 2003. But experts think it is too early to conclude the epidemic is in retreat there.