[Maurice Tift]

how come most of the dead have been between the ages of 15-49?

   I don't think there are many old people in Africa. I did a google search and found an age distribution table.

[ncountylee]

The young and elderly pack less fudge?

[DB]

15-49 makes sense to me.

They probably start having sex at 12 or 13 and it takes a few years before they die from the disease they acquire from it. On top of that there are very few Africans older than 49. So the dying include all ages that are sexually active. As more die, the average age of the dead will get younger and younger because there won't be anyone older to infect.