In Uganda, risk factors for recent HIV infection include being female, having had multiple sex partners in the past year, being widowed or divorced, having a herpes simplex virus type-2 (HSV-2) infection and (among men) being uncircumcised, according to findings from a nationally representative survey.¹ In addition, among married individuals who have sex with outside partners, condom use is associated with a substantially reduced risk of recent infection. Although the researchers did not track changes in individuals' HIV status over time, they were able to identify probable recent (as opposed to long-term) infections on the basis of respondents' antibody levels, and their findings suggest that as many as 15% of HIV-positive individuals had been infected only recently (a median of six months prior to the survey).

The findings come from the 2005 Uganda HIV/AIDS Sero-Behavioral Study, in which a nationally representative sample of individuals aged 15–59 were interviewed about their health and sexual behavior. All residents of selected households, as well as persons who had visited the night before the survey, were eligible to participate. The interview included questions about respondents' age at first sex, number of recent and lifetime partners, STI history and demographic variables. In addition, respondents provided a blood sample, which was tested for HIV, syphilis and HSV-2. Because the study was primarily concerned with recent HIV infections, rather than with all HIV infections, the researchers used a test that measures the proportion of an individual's immunoglobulin G antibodies that react against HIV; this proportion increases in a predictable manner following infection, providing a means to estimate the recency of infection. The researchers used multivariate logistic regression to assess associations between interview variables and respondents' HIV status.

Researchers visited 9,529 households and completed interviews with 95% of eligible women and 89% of eligible men; 94% of those who completed the interviews provided blood samples. The final sample consisted of 10,227 women and 8,298 men. Tests revealed that 6% of these individuals were infected with HIV, and 15% of the infections were classified as recent (within a median of six months prior to the survey), yielding an incidence of 1.8 infections per 100 person-years. The incidence was 2.1 infections per 100 person-years among female respondents and 1.5 per 100 person-years among males, and it was higher among persons who were widowed (4.8) or divorced (3.0) than among those who were married (2.0) or had never been married (0.7). The incidence among individuals aged 15–24 (1.1) was about half that among those aged 25–59 (2.3).

Multivariate analyses revealed that the odds of recent HIV infection were greater among women than among men (odds ratio, 2.4), among widowed (6.1) or divorced (3.0) individuals than among those who had never married, and among persons with one (1.7) or two or more (2.9) sex partners in the past year than among those who had not had any partners. Risks were also elevated among individuals who tested positive for HSV-2 (3.9), had had an STI in the past year (1.7) or were not circumcised (2.5; the odds for women were similar to those of circumcised men). Risk varied by region as well: Compared with those who lived in the central/Kampala region, those who lived in the north central area had a higher risk (2.6), while those who lived in the west Nile area had a lower risk (0.3). The findings were generally similar when the researchers used a more stringent definition of recency (i.e, a lower proportion of antibodies against HIV). Age, education and lifetime number of partners, among other characteristics, were not associated with the risk of recent infection.

In multivariate analyses restricted to sexually active, married respondents, the odds of a recent HIV infection among individuals who did not use a condom the last time they had sex with a nonmarital partner were three times those of respondents who had no nonmarital partners (odds ratio, 3.3). In contrast, respondents who had had one or more nonmarital partners, but had used a condom with at least one of them, did not have increased odds of a recent infection. As they were for the sample as a whole, the odds of recent infection among sexually active, married respondents were elevated among those who tested positive for HSV-2 (4.1), had had an STI in the past year (1.6) or were not circumcised (4.1). For 74 married respondents with recent HIV infections, test results were also available for their spouses; 38% of the spouses had long-standing infections, 14% had recent infections and 49% were not infected.

The authors note that the incidence of recent infections in the total sample was higher than expected given the 6% prevalence of HIV in Uganda. This could reflect a recent increase in transmission rates, though it might be an artifact of the screening method. The elevated incidence of recent infections among females, divorcees and widows may be attributable to social factors—such as power differentials between the sexes and women's limited access to education and financial resources—that restrict women's ability to protect themselves from HIV, and highlights "the potential benefit of focusing specific interventions on changing social norms." The findings also point to the continued need for HIV prevention efforts that focus on reducing individuals' number of sexual partners, promoting condom use, HIV testing and circumcision, and delaying sexual debut. Finally, the elevated risk observed among individuals with HSV-2 suggests that drugs that suppress the virus, such as acyclovir, might help reduce HIV risk.—P. Doskoch

REFERENCE

1. Mermin J et al., Risk factors for recent HIV infection in Uganda, Journal of the American Medical Association, 2008, 300(5):540–549.