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High prevalence of HIV infection among youth in a South African mining town is associated with HSV-2 seropositivity and sexual behaviour
Bertran Auvert, Ron Ballard, Catherine Campbell, Michel CaraŽl, Matthieu Carton, Glenda Fehler, Eleanor Gouws, Catherine MacPhail, Dirk Taljaard, Johannes Van Dam, Brian Williams
AIDS Volume 15, number 7, p.
In this study published in AIDS, the authors found an extremely high prevalence of HIV among young women (34%) and men (9%) aged 14-24 years from a township in the Carletonville district of South Africa. HIV prevalence among women aged 24 was 66%, one of the highest rates ever reported in a general population. The authors suggest that these remarkable findings are due to high rates of HIV transmission from men to women, and the major role played by HSV-2 (herpes simplex virus type 2) in the spread of HIV in this population.
South Africa is experiencing one of the most rapidly growing HIV epidemics in the world. In 1990 the prevalence of HIV infection among women attending antenatal clinics was less than 1%. By the end of 1999 national prevalence had reached 23%. Most of the studies that have been performed in sub-Saharan Africa to date have investigated risk factors for HIV infection among adults, but young people, and especially young women, are at particularly high risk of HIV infection in many developing countries.
The authors claim that the high prevalence of HIV infection among young women compared to young men in the Carletonville study is not simply due to either very high rates of infection amongst their partners or to very high levels of sexual activity. In fact, in almost all surveys carried out across Eastern and Southern Africa by the World Health Organization, men report a higher turnover of partners before marriage thanwomen, and in this study the mean number of partners was 4.7 for men and 2.6 for women.
One reason for this discrepancy in HIV prevalence between young men and young women is that HIV is more easily transmitted from men to women than from women to men. Studies in industrialized countries have shown that, in the absence of other risk factors, men are two to three times more likely to transmit HIV to women than vice versa. However, the estimates of transmissibility of HIV from men to women in the Carletonville study are significantly higher than this, even taking into account the possibility of women under-reporting their number of sexual partners. There are several possible explanations for this. A recent study has shown that viral load is an important predictor in the risk of heterosexual HIV transmission, and viral loads are likely to be higher in South Africa than in Europe or the US due to the reduced availability of effective drugs and treatment. Another factor may be the high prevalence of HSV-2 (herpes simplex virus type 2) in this population, as HSV-2 can facilitate HIV infection.
In the Carletonville study HSV-2 status was the most significant factor associated with HIV status for both men and women. For example, men infected with HSV-2 were seven times more likely to also be HIV positive than those who did not have HSV-2. HSV-2 acts as a co-factor in HIV transmission by causing genital ulcers which both increase the susceptibility of the uninfected to infection by HIV, and increase the infectivity of those who already carry the virus.
Reducing HIV transmission in this population is a major challenge. At the present time genital herpes can only be treated at considerable cost, and no vaccine is currently available. Therefore the best options for reducing transmission include communication campaigns aimed at alerting the population to the relatively mild manifestation of genital herpes and the need to abstain from sexual contact while lesions persist. In addition it is important to find ways to persuade young people to reduce their number of sexual partners and, most importantly of all, to substantially increase condom use; in this study, 41% of men and 42.5% of women reported never having used condoms. As most young people in this study were still at school when they had their first sexual experience, attempts to limit the future spread of HIV should involve not only prevention in the community but also effective school-based interventions as an essential part of the school curriculum.
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