This chapter examines two sets of factors making cholera a high risk. First, changing ecological conditions in Lakes Chad, Tanganyika, and Malawi (Nyasa) have enabled cholera to become free-standing and thus endemic to thousands of people living in these large lake basins. The second set involves armed conflict and the ensuing dispersal of refugees, and how these factors have exposed people to cholera in the DRC and in Mozambique.

THE LAKE CHAD BASIN

Lake Chad is a large, shallow lake in the heart of the vast West African Sahel. It is a major source of water and fish for more than twenty million people in the four countries touching its shores: Cameroon, Chad, Niger, and Nigeria. More than 90 percent of its water comes from the Chari River, originating to the south in the tropical forest of the Central African Republic (CAR).

Lake Chad has experienced dramatic environmental cycles of expansion and contraction over the past thirteen millennia. Recently, its diminution has accelerated, from an area of 26,000 square kilometers in 1960 to less than 1,500 square kilometers in 2000, with an exceptionally shallow average depth of only one and a half meters. Experts attribute this shrinkage to a combination of factors: cyclical patterns of reduced rainfall in what is an arid part of Africa; greatly increased amounts of irrigation water drawn from the Chari River system; and population growth, which has dramatically increased water demand in the past half century.