From UNAIDS

A little more than 10%of the world’s population live in sub-Saharan Africa but it is home to almost 64% of all people living with HIV: 24.5 million [21.6
million–27.4 million]. Two million [1.5 million–3.0 million] of them are children younger than 15 years of age. Indeed, almost nine in ten children (younger than 15 years) living with HIV are in sub-Saharan Africa. An estimated 930 000 [790 000–1.1 million] adults and children died of AIDS in southern Africa in 2005 - one-third of all AIDS deaths globally. Access to anti-retroviral therapy has increased more than eight-fold since the end of 2003, with
about 810 000 people on treatment in December 2005. About one in six (17%) of the 4.7 million people in need of anti-retroviral therapy in this region now receive it. Progress is uneven, however, with coverage reaching or exceeding 50% in only three countries (Botswana, Namibia and Uganda) but remaining below 20% in most others. South Africa accounts for one-quarter of all people receiving anti-retroviral therapy in sub-Saharan Africa (WHO/UNAIDS, 2006).

Altogether, there are now 16 African countries in which more than one-tenth of the adult population aged 15 - 49 is infected with HIV. In seven countries, all in the southern cone of the continent, at least one adult in five is living with the virus. In Botswana, 24% of adults are now HIV-infected with 38.5% of women attending ante-natal clinics being HIV-positive.

Similar numbers exist elsewhere: 

Lesotho - 23% of the adult population infected with 28.4% of women attending ante-natal clinics being HIV-positive
South Africa - 19% of the adult population infected with 29% of women attending ante-natal clinics being HIV-positive

Three-quarters of all women (15 years and older) living with HIV are in sub-Saharan Africa. In most of the region, women are disproportionately affected by AIDS, compared with men - expressions of the often highly unequal social and socioeconomic status of women and men. Women comprise an estimated 13.2 million [11.4million–15.1 million] - or 59% - of adults living with HIV in Africa south of the Sahara.

South Africa has the largest number of people living with HIV/AIDS in the world: An estimated 5.5 million [4.9 million - 6.1 million] people were living
with HIV in 2005. It has been reported that more than 90% of the truck drivers entering South Africa from Zimbabwe are HIV-positive.

While West and Central Africa are relatively less affected by HIV infection, the prevalence rates in some large countries are creeping up: for example, Cameroon  has an infection rate of 4.9 - 5.9%

However, in some countries the infection rate remains quite low (e.g. Senegal  (1%) and Mali (1.7%)) but in these countries the rate is also increasing.

There has been a particularly sharp rise in the infection rate of pregnant women in Cameroon where the rate of 11.8% in 2001 has more than doubled since 1998. In Nigeria, the most populous country in sub-Saharan Africa, over 5.8% of adults have HIV. The prevalence rate in most other West African countries remains below 3%. 

Infection rates in East Africa, once the highest on the continent, hover above those in the West of the continent but have been exceeded by the rates now being seen in the southern cone. The prevalence rate among adults in Ethiopia and Kenya has reached double-digit figures and continues to rise. Particularly impressive has been the situation in Uganda which has seen a drop in infection rates due to increased use of condoms and delayed sexual intercourse.