Kenyan slum dwellers from the sprawling Mathare slums walk next to a river of sewerage near the capital Nairobi. Kenyan slum dwellers from the sprawling Mathare slums, one of the largest and poorest slums in Africa, walk next to a river of sewerage near the capital Nairobi, August 31, 2005. Nearly a third of Nairobi's 3 million people live in the slums that are often surrounded by garbage and waste which cause diseases. REUTERS/Antony Njuguna