July 2002, Vol. 8, No. 1

Epidemiology
What Factors Affect the Prevalence of HIV in Sub-Saharan Africa?

More than 3 million of the 5 million people who were newly infected with HIV in 2001 live in sub- Saharan Africa, according to UNAIDS. The vast majority of HIV-infected adults in Africa acquired their infection through heterosexual intercourse. Over the decades since the AIDS epidemic was first noted, researchers have observed that the prevalence of HIV infection within Africa varies greatly. While many areas in East and Southern Africa experience high rates of infection, regions in West and Central Africa generally have lower infection rates. A number of theories to explain these disparities have been put forth. But until now there have been no systematic studies to directly address this matter. 

Two Population Council researchers, Jane Chege, then based in Nairobi, Kenya, and Naomi Rutenberg, based in Washington, DC, participated along with several other investigators in a recent study on HIV. Chege is now based in Johannesburg, South Africa. The findings of the investigation, known as the multicentre study of factors determining the different prevalences of HIV in sub-Saharan Africa, were presented in a special supplement to the journal AIDS. The Population Council collaborated on the study design and questionnaires and collected data in one location, Kisumu, Kenya. Chege and Rutenberg assessed data quality and analyzed data at the population and individual level. This analysis suggested further avenues of investigation, which were pursued by the other scientists. The research findings indicate that changes in HIV-prevention policy are urgently needed. 

The researchers investigated HIV epidemics in four cities. Two of these cities—Kisumu and Ndola, Zambia, in East and Southern Africa—have high HIV prevalence. And two—Cotonou, Benin and Yaoundé, Cameroon, in West and Central Africa—have a low and stable HIV prevalence. In each of these cities, researchers selected approximately 1,000 men and 1,000 women aged 15–49 years from the general population. Those who agreed to participate were interviewed about sexual behaviors and other factors that might influence their susceptibility to HIV infection. They were tested for HIV and a number of other sexually transmitted infections (STIs). 

HIV prevalence in young women 
The HIV testing conducted as part of the study confirmed a high HIV prevalence in Kisumu and Ndola. It also underlined the greater risk of infection experienced by women, particularly young women, compared to men. 

A group of researchers, including Chege, analyzed the statistics from Kisumu and Ndola. They found that among sexually active 15–19-year-olds in both sites, HIV was six times more prevalent in women than in men. Among 20–24-year-olds, the infection was three times more prevalent in women. HIV was equally widespread among women and men in the 25–49 year age group. 

Behavioral factors did not seem to explain this difference in HIV susceptibility. The presence of other STIs, especially ones that result in ulcerated lesions, may account for some increased transmission of HIV. In both cities, for example, the rate of infection with herpes simplex virus type 2 was roughly four times greater among young women than among young men. Even when no other STI was present, however, young women were still at higher risk for HIV infection. There is evidence of high rates of HIV positivity following only a few episodes of sexual intercourse, suggesting that young women have a high susceptibility to infection. 

Male circumcision 
The exposure of mucosal surfaces to HIV-containing secretions may account for another discrepancy in HIV prevalence seen in sub-Saharan Africa. A growing body of research shows that uncircumcised men in sub-Saharan Africa are about twice as likely as circumcised men to be infected with HIV. The foreskin of the penis, which is removed during circumcision, is lined with a mucous membrane. The prevalence of male circumcision varies across the continent. In Yaoundé and Cotonou nearly all men studied were circumcised. In Kisumu, roughly 28 percent of men studied were circumcised and in Ndola the figure was only 9 percent. 

The researchers found three HIV risk factors that were more prevalent in Kisumu and Ndola than in Cotonou and Yaoundé: being married or having been married (among women and men), lack of circumcision (among men), and increased infection with herpes simplex virus type 2 (among women). The HIV risk associated with marriage may reflect the exposure of men and women, through repeated sexual intercourse, to spouses infected with HIV. 

The investigators found a strong protective effect of male circumcision in Kisumu. The prevalence of HIV, herpes simplex virus type 2, and syphilis was significantly lower in circumcised men there. 

The researchers conclude that the evidence of circumcision’s protective effect against HIV is convincing and that the provision of safe male circumcision should be considered as part of the public health strategy to reduce the spread of HIV. “But more research is needed to determine acceptability, feasibility, and cost-effectiveness,” assert the investigators. Moreover, interventions to introduce circumcision must be carefully evaluated as they proceed. 

The Population Council’s Horizons program recently developed a research agenda on male circumcision that should contribute to feasibility studies. USAID-funded Horizons research is conducted in collaboration with the International Center for Research on Women, the Program for Appropriate Technology in Health, the International HIV/AIDS Alliance, Tulane University, Family Health International, and Johns Hopkins University. 

Key implications 
In addition to highlighting the urgent need for more research and policy development regarding male circumcision, the study’s findings suggest other key changes, say the researchers. “Infection with herpes simplex virus type 2 and HIV are extremely prevalent in young women shortly after they begin sexual activity,” says Chege. “Policymakers should strengthen community and school-based peer education for young women and men before they start sexual activity.” 

Additionally, “because HIV is likely to be transmitted between spouses, voluntary HIV counseling and testing among couples, particularly before marriage, should be encouraged,” says Rutenberg. The researchers also called for community-based education to help people recognize the symptoms of herpes simplex virus type 2. During outbreaks, people infected with this virus can temporarily abstain from sex or use condoms in order to reduce transmission.

Sources
Auvert, B., A. Buvé, B. Ferry, M. Caraël, L. Morison, E. Lagarde et al. 2001. “Ecological and individual level analysis of risk factors for HIV infection in four urban populations in sub-Saharan Africa with different levels of HIV infection,” AIDS 15(suppl 4): S15–S30. 

Auvert, B., A. Buvé, E. Lagarde, M. Kahindo, J. Chege, N. Rutenberg et al. 2001. “Male circumcision and HIV infection in four cities in sub-Saharan Africa,” AIDS 15(suppl 4): S31–S40.

Buvé, A., M. Caraël, R.J. Hayes, B. Auvert, B. Ferry, N.J. Robinson et al. 2001. “The multicentre study on factors determining the differential spread of HIV in four African cities: Summary and conclusions,” AIDS 15(suppl 4): S127–S131. 

Glynn, J.R., M. Caraël, B. Auvert, M. Kahindo, J. Chege et al. 2001. “Why do young women have a much higher prevalence of HIV than young men? A study in Kisumu, Kenya and Ndola, Zambia,” AIDS 15(suppl 4): S51–S60. 

van Dam, Johannes and Marie-Christine Anastasi. 2000. “Male circumcision and HIV prevention: Directions for future research.” Horizons Project Report. Washington, DC: Population Council. (full text)

Outside funding
Institute of Tropical Medicine, Antwerp and UNAIDS

(Return to issue contents)