AIDS in Africa: A Regional Overview

By Hawlan Ng

"The network of roads in Botswana is one of the best I’ve seen in Africa," says Dr. Ibou Thior, a Harvard AIDS Institute researcher. "Citizens have become more mobile than ever—but as a result, unfortunately, so has the virus." Thior works with pregnant women in Botswana, helping to prevent the transmission of HIV to their infants. The positive effects that economic growth has brought this southern African nation have been weakened by a parallel growth in HIV prevalence, with at least one in four adults infected. Thior says, "Now, people spend most of their weekends attending funerals."

The spread of HIV in southern Africa is occurring at much greater speed than in other parts of the continent. For instance, in the western African nation of Senegal, where strong, sustained prevention campaigns have kept the virus under relative control, HIV has infected only 1 to 2 percent of the general population.

The vast differences in the rates of HIV infection from one region of the continent to another reflect socioeconomic and cultural differences, according to WafaieFawzi, assistant professor of international nutrition and epidemiology at the Harvard School of Public Health. Fawzi is collaborating with researchers in Dar es Salaam, the capital of Tanzania, to find ways to block perinatal transmission of HIV. Fawzi has seen how regions of the continent have been affected in different ways. "There are multiple differences between the northern and the southern, eastern, and central parts of the continent that could contribute to the higher burden of HIV in the latter regions. Differences in behavior, prevalence of sexually transmitted diseases, levels of malnutrition, access to health care, and viral subtypes may explain this variation."

In Southern Africa, a Dire Situation
Earlier in the epidemic, HIV was not as well established in southern Africa as it was in central and eastern Africa. But today the highest rates of HIV incidence in the world are found in the three-nation cluster of Namibia, Botswana, and Zimbabwe. South Africa, where rates of infection were once lower than those in surrounding countries, is now home to one in seven of Africa’s new infections.

The specific viral subtype responsible for the epidemic in southern Africa—subtype C of HIV-1, the more virulent form of HIV—has been postulated by Harvard AIDS Institute researchers to be more easily transmitted through sexual activity between men and women than are other subtypes. Heterosexual transmission is responsible for the majority of new HIV infections in this region, while mother-to-infant transmissions represent the area’s second most common mode of infection. In some towns in southern Africa, 50 percent of women who are pregnant are infected with HIV. At least one-third of these women are likely to transmit the infection to the children they carry.

New Subtypes Emerge in Central and Eastern Africa
Within Africa, AIDS was first detected in populations in the continent’s central region, but the disease, and the incidence of HIV, have moved quickly south and east. In most nations in central Africa, prevalence is now relatively moderate, with 2 to 4 percent of adults living with HIV or AIDS, according to a 1998 report of the United Nations Joint Programme on HIV/AIDS (UNAIDS).

"HIV rates appear to have plateaued very early in central Africa, by the mid-to-late 1980s," says Max Essex, chair of the Harvard AIDS Institute. Essex, who has led teams of researchers to Africa to study the impact of the virus there, has noted that rates among young adults in some nations in the central region are lower than expected. In nations such as Rwanda and Burundi, however, rates have increased, possibly fueled by their years of civil unrest.

Infection rates in urban areas of central Africa at one time dwarfed those in villages and rural areas. But as migration to and from cities increased, rates in rural areas and small villages reached those of urban levels. "Much of this can be attributed to men working and patronizing sex workers in the cities, then bringing the virus home to their families in the countryside," says Essex.

Whereas HIV-1 subtypes A, C, and D are responsible for most HIV infections in Africa, other HIV-1 subtypes, such as F, G, H, I, J, O, and U, have been emerging in Cameroon and Gabon. To date, the overall prevalence of these subtypes is quite low.

"It seems to be a place where new viruses have entered the human population for the first time," notes Essex.

In eastern Africa, subtypes A and D predominate, but the more virulent subtype C is beginning to make its presence felt. High rates of new infections have been linked to high-risk activity along highways between the major cities; many of those traveling along the roads regularly visit sex workers.

Essex believes that subtype C is spreading up from the south, causing higher incidence rates in countries such as Tanzania. "Although rates in eastern Africa have plateaued or even gone down a little bit in the past five years, things could change as subtype C moves into the region," he says.

In Tanzania, Harvard AIDS Institute researchers studying mother-to-infant transmission have found evidence that certain intersubtype recombinants of the virus are transmitted more effectively from mothers to their infants—a finding with ominous implications for the future spread of HIV.

In Western Africa, Prevention Efforts Yield Results
Compared with other regions of Africa, HIV has a relatively modest presence in western African nations such as Senegal, Mauritania, and Cape Verde. Many attribute the lower prevalence of HIV in Senegal to the strong influence of Islam there, as well as to active prevention programs sponsored by the government and other social institutions.

"People in general recognize that there is an epidemic," says Thior. "There are many efforts through education, the media, and by people coming forward to talk about their experiences, as well as through cooperation from religious leaders. It is important to have the support of religious institutions because they have historically been reluctant to talk about sex, but people have been more receptive because these institutions are engaged in the effort to stop HIV."

HIV-2, a rarer, less virulent form of HIV, was discovered in Senegal in 1985 by members of a research collaborative that included Harvard AIDS Institute scientists. Most of the world’s 500,000 cases of HIV-2 have been found in western Africa. The highest rates of this form of HIV occur in Guinea Bissau. This second AIDS virus has largely remained within the population in which it was first isolated, that of female sex workers, in part because of prevention campaigns that have helped curtail its spread.

Northern Africa Faces the Need for Action
The nations of Morocco, Algeria, Libya, and Egypt have thus far escaped the level of devastation experienced in the eastern and southern regions of Africa. Although exact figures have been difficult to come by, prevalence in this region has been estimated at below 1 percent. That may begin to change, however, as the long-term effects of such high-risk behaviors as sex tourism and injection drug use begin to make their presence felt. This figure may also begin to reflect the increases in prevalence often associated with population fluxes, such as those that occur with the large populations of immigrant workers who help satisfy the region’s labor needs.

Prevention efforts in these nations have been increasing and governments have been receptive to the actions that communities and non-governmental organizations have been taking to educate their populations, particularly groups at high risk for infection.

With the continued spread of HIV, Africa faces an uncertain future. Without sustained intervention, the continent’s promising economic potential will be undermined by the tragic loss of generations. Says Thior, "If the current trend continues or becomes worse, we will have a society consisting mostly of orphans and the elderly."

—Hawlan Ng is a contributing writer to the Harvard AIDS Review.