[From The Economist] AIDS in Africa:

Just as the bubonic plague upturned the social order in medieval Europe, AIDS will reshape Africa. But how?
[...] Among the many ways that AIDS is destabilising the continent, perhaps the most worrying is the exploding population of orphans. Those who die of AIDS often leave children behind, most of whom are not infected. Counting all those under 15 years who have lost at least one parent, Africa already had 34m orphans last year. By the end of the decade, that is predicted to rise to 42m, half because of AIDS.