by Brian O’Reilly

About the author: Brian O'Reilly is on the Board of Editors at Fortune magazine.

At a trade show in Botswana, one of the most prosperous countries in Africa, a well-dressed crowd gathers to celebrate. The party, hosted by the De Beers- Botswana diamond monopoly, has attracted the nation’s best and brightest: Miss Botswana Universe, business leaders, government ministers. They sip chardonnay and chatter with the aplomb of Manhattan socialites. In conversation, a television anchor calmly dismisses the extent of the AIDS epidemic in Botswana and disputes whether HIV even causes AIDS. Amid the good cheer, a jarring thought intrudes: Half the people in the room will probably be dead in five years.

The HIV/AIDS epidemic moving through Africa is unlike any plague the world has ever seen...