Heterosexual anal sex and first sexual exposure associated with high rates of HIV transmission in African youth

Christopher Gadd, Michael Carter
Published: 16 July 2004

Young Africans are becoming infected with HIV through unprotected anal sex between men and women, and often on their first sexual encounter, according to two presentations at the Fifteenth International AIDS Conference in Bangkok. The two studies, presented in a ‘late breaker’ session on the conference’s final full day, support calls for earlier educational interventions, to reduce the spread of the virus.

A role for anal sex?

Recent studies have suggested that anal sex is more common in southern Africa and has played a more important role in the spread HIV than previously thought. It has been suggested that in the past both investigators and individuals participating in research have been reluctant to discuss this sexual activity.

Investigators, based at the University of California, San Francisco developed a model to predict the prevalence of anal sex and its role as a risk factor for HIV infection using answers provided in a behavioural interview by 1109 young South Africans aged between 15 and 24 years.

Logistic regression was used to predict HIV infection as an outcome from four sexual activities:

  • Vaginal sex only.
  • Anal and vaginal sex.
  • More than two lifetime sexual partners.
  • The use of a condom during the last episode of sexual intercourse.

HIV prevalence in the sample was high, at 21%. After controlling for types of sexual intercourse, numbers of lifetime partners, and condom use at the last sexual intercourse, investigators noted that individuals reporting both anal and vaginal sex had an elevated risk of HIV infection, particularly in men.

Women reporting both anal and vaginal sex had a greater risk of HIV infection (odds ratio [OR] 12.8, 95% CI 8.8 – 19.0) than women who only reported vaginal sex (OR 9.5, (5% CI 7.3 – 12.3), although this difference was not statistically significant.

However, men who reported both anal and vaginal sex (OR 6.0, 95% CI 3.5 – 10.5) had an elevated risk for HIV infection compared to men who reported only vaginal sex (OR 3.2, 95% CI 2.3 – 4.6). Although the investigators did not ask the interviewees the gender of their sexual partners, they were able to deduce that only around 7% of the men had had sex with another man, concluding that insertive heterosexual anal sex is a significant risk factor for young South African men.

“Anal sex contributes to the population risk of HIV infection in South Africa,” concluded the presenter, Dr. Tim Lane. He added that current HIV prevention strategies “may unwittingly encourage misconceptions about the relative safety of anal sex.” Data suggest that condoms were not used as consistently for anal sex as vaginal sex, and the investigators suggest that future studies should compare the consistency of condom use for anal and vaginal sex. These studies should also seek to quantify anecdotal reports that anal sex is used by young people as both a form of birth control and as a means of reducing HIV risk.

Infection during the first sexual encounter

In the second presentation, results of a survey carried out in Asembo, Western Kenya between 2002 and 2003 were presented. They showed that many women in this population start having sex at a young age, and are exposed to high rates of HIV infection.

After interviewing a random selection of 13- to 34-year olds about their sexual behaviour and testing them for HIV, herpes simplex virus 2 (HSV2) and pregnancy, the investigators found that 42% of the 540 women under 20 reported ever having had sex, with a mean age for the first sexual experience being 16.5 years.

Remarkably, 8% of the women had first had sex before the age of 13, and 15% before their first menstruation. The majority of the 195 sexually active, never married women reported that their first sexual experience was consensual, and with a man aged under 20 (78% and more than 80%, respectively).

However, only 27% of the women reported using a condom during their first sexual experience.

A worrying 4.7% (95% CI 0.7 - 8.7) of the 106 sexually active women who had had only one partner were infected with HIV, and 12.5% (95% CI 6.1 – 18.9) with HSV-2. The majority of the HIV infections were found to occur between the ages of 16 and 17, which coincides with the reported age of first sexual experience.

The presenter, Dr. H. Vandenhoudt, used these data to estimate that among all first-time partners in this setting, HIV prevalence was between 1.3 and 3.3%, and HSV-2 prevalence between 11.5 and 14.0%.

She concluded that “prevention efforts should target pre-teens before they become sexually active,” calling for targeting of girls between the ages of nine and twelve years, and the involvement of parents, guardians and community-based schemes in sexual health and HIV prevention education schemes.

References

Lane T et al. Anal sex as a risk factor for HIV infection among young people aged 15-24 in South Africa: data from a nationally representative household survey. XV International AIDS Conference, Bangkok, abstract LbOrC21, 2004.

Vandenhoudt H et al. First sexual intercourse and exposure to HIV infection among young women in a high HIV prevalence area in Western Kenya. XV International AIDS Conference, Bangkok, abstract LbOrC22, 2004.