Sub-Saharan Africa

Source: 2008 report on the global AIDS epidemic

An estimated 1.9 million people were newly infected with HIV in sub-Saharan Africa in 2007, bringing to 22 million the number of people living with HIV. Two thirds (67%) of the global total of 32.9 million people with HIV live in this region, and three quarters (75%) of all AIDS deaths in 2007 occurred there.

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).

Recent epidemiological trends

Most epidemics in sub-Saharan Africa appear to have stabilized, although often at very high levels, particularly in southern Africa. Additionally, 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.

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 favourable behaviour changes and signs of declining HIV prevalence among women using antenatal services in some urban areas.

HIV data from antenatal clinics in South Africa suggest that the country’s epidemic might be stabilizing, but there is no evidence yet of major changes in HIV-related behaviour. 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. In some of the provinces in the central and southern zones of the country, adult HIV prevalence has reached or exceeded 20%, while infections continue to increase among young people (ages 15–24).

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 (from 12% to 16% for women and 29% to 36% for men). 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. In Côte d’Ivoire, HIV prevalence among pregnant women in urban areas fell from 10% in 2001 to 6.9% in 2005. The largest epidemic in West Africa—in Nigeria, the continent’s most populous country—appears to have stabilized at 3.1%, according to HIV infection trends among women attending antenatal clinics.

Main modes of HIV transmission

Heterosexual intercourse remains the epidemic’s driving force in sub-Saharan Africa. The high rate of sexual transmission has also given rise to the world’s largest population of children living with HIV. However, recent epidemiological evidence has revealed the region’s epidemic to be more diverse than previously thought.

Heterosexual intercourse related to serodiscordant couples

According to Demographic and Health Surveys in five African countries (Burkina Faso, Cameroon, Ghana, Kenya, and the United Republic of Tanzania), two thirds of HIVinfected couples were serodiscordant, that is only one partner was infected. Condom use was found to be rare: in Burkina Faso, for example, almost 90% of the surveyed cohabiting couples said they did not use a condom the last time they had sex.

A separate, community-based study in Uganda has shown that, among serodiscordant heterosexual couples, the uninfected partner has an estimated 8% annual chance of contracting HIV. Strikingly, in about 30% – 40% of the serodiscordant couples surveyed, the infected partner was female. Indeed, it appears that more than half of the surveyed HIV-infected women who were married or cohabiting had been infected by someone other than their current partner.

Sex work

Sex work is an important factor in many of West Africa’s HIV epidemics. More than one third (35%) of female sex workers surveyed in 2006 in Mali were living with HIV, and infection levels exceeding 20% have been documented among sex workers in Senegal and Burkina Faso. Sex work plays an important, but less central, role in HIV transmission in southern Africa, where exceptionally high background prevalence results in substantial HIV transmission during sexual intercourse unrelated to sex work.

Injecting drug use

Injecting drug use is a factor to some extent in several of the HIV epidemics in East and southern Africa, including Mauritius, where the use of contaminated injecting equipment is the main cause of HIV infection. In various studies, about half of the injecting drug users tested in the Kenyan cities of Mombassa (50%) and Nairobi (53%) were HIV positive.

Sex between men

Several recent studies suggest that unprotected anal sex between men is probably a more important factor in the epidemics in sub-Saharan Africa than is commonly thought. In Zambia, one in three (33%) surveyed men who have sex with men tested HIV-positive. In the Kenyan port city of Mombasa, 43% of men who said they had sex only with other men were found to be living with HIV. HIV prevalence of 22% was found among the 463 men who have sex with men who participated in a study in Dakar, Senegal.