An estimated 1.9 million people were newly infected with HIV in sub-Saharan Africa in 2007. In total, 22 million people are living with HIV in the region, which is two thirds (67%) of the global population of people with HIV. Most epidemics in Sub-Saharan Africa appear to have stabilized (some at very high levels, such as in southern Africa). In a growing number of countries, adult HIV prevalence appears to be falling. For the region as a whole, women are disproportionately affected in comparison with men, with especially stark differences between the sexes in HIV prevalence among young people.

Sub-Saharan Africa's epidemics vary significantly from country to country in both scale and scope. Adult national HIV prevalence is below 2% in several countries of West and Central Africa, as well as in the horn of Africa, but in 2007 it exceeded 15% in seven southern African countries (Botswana, Lesotho, Namibia, South Africa, Swaziland, Zambia, and Zimbabwe), and was above 5% in seven other countries, mostly in Central and East Africa (Cameroon, the Central African Republic, Gabon, Malawi, Mozambique, Uganda, and the United Republic of Tanzania).

In southern Africa, reductions in HIV prevalence are especially striking in Zimbabwe, where HIV prevalence in pregnant women attending antenatal clinics fell from 26% in 2002 to 18% in 2006. In Botswana, a drop in HIV prevalence among pregnant 15-19-year-olds (from 25% in 2001 to 18% in 2006) suggests that the rate of new infections could be slowing. The epidemics in Malawi and Zambia also appear to have stabilized, amid some evidence of favorable behavior changes and signs of declining HIV prevalence among women using antenatal services in some urban areas.

In South Africa, the estimated 5.7 million South Africans living with HIV in 2007 make this the largest HIV epidemic in the world. Meanwhile, the 26% HIV prevalence found in adults in Swaziland in 2006 is the highest prevalence ever documented in a national population-based survey anywhere in the world. In Lesotho and parts of Mozambique, HIV prevalence among pregnant women is increasing. Some of the provinces in the central and southern zones of the country, report adult HIV prevalence exceeding 20%.

HIV prevalences in the comparatively smaller epidemics in East Africa have either reached a plateau or are receding. After dropping dramatically in the 1990s, adult national HIV prevalence in Uganda has stabilized at 5.4%. However, there are signs of a possible resurgence in sexual risk-taking that could cause the epidemic to grow again. For example, the proportion of adult men and women who say they had sex with a person who was not a spouse and did not live with the respondent has grown since 1995.

Most of the comparatively smaller HIV epidemics in West Africa are stable or are declining - as is the case for Burkina Faso, Côte d'Ivoire, and Mali. The largest HIV epidemic in Western Africa, in Nigeria, appears to be stabilizing at 3.1%, according to surveys of HIV infection from antenatal clinics.