Subsaharan Africa has the largest epidemic of HIV, that is why. Because you need a control group and compare the frequency of new infections.
It would make no sense to study HIV drugs in, say, Egypt, where the sexual mores are rather strict due to the conservative Islamic character of the society, and thus infection rates remain very low.
(Note that Egypt is also Africa, but probably the "wrong kind of"... at least as far as the fashionable racial classifications go.)
Subsaharan Africa has the largest epidemic of HIV, that is why. Because you need a control group and compare the frequency of new infections.
It would make no sense to study HIV drugs in, say, Egypt, where the sexual mores are rather strict due to the conservative Islamic character of the society, and thus infection rates remain very low.
(Note that Egypt is also Africa, but probably the "wrong kind of"... at least as far as the fashionable racial classifications go.)