CROI: Married people should be primary target for HIV prevention in Uganda, national study shows

Uganda has undergone a striking change in the profile of people becoming newly infected, with older and married individuals now making up the vast majority of new infections, according to findings from a national study of HIV incidence conducted in 2004-5 and presented last week at the Fifteenth Conference on Retroviruses and Opportunistic Infections in Boston.

Eighty per cent of new infections are now occurring in rural Uganda, said Wolfgang Hladik of the US Centers for Disease Control Uganda programme.

The findings were first discussed publicly at an international scientific meeting last June, when David Apuuli of the Ugandan AIDS Commission described how Uganda’s government has had to re-orient its HIV prevention policy to focus on married couples, concurrent partnerships and HIV-discordant long-term partnerships as a result of the study.

From 2004 to 2005, a population-based, nationally representative survey took place among adults aged 15 to 59 years. Of 21.400 eligible residents, 90% of the women and 84% of the men agreed to give blood specimens, resulting in 18,525 samples.

HIV was found in 1,092 of the specimens, of which 172 (17%) were identified as recent infections. (BED IgG capture-based ELISA was used to identify seroconversion that had occurred within the past 155 days). The weighted incidence of infection was 1.9 per 100 person-years.

Using a multivariate logistic regression model, researchers determined that 112 (63%) of all recent infections occurred in individuals who were married; 45 (27%) among individuals divorced or widowed, and 15 (9%) among single persons. Interestingly, just 40 (23%) of all new infections were in persons 25 years old or younger.

The analysis also identified risk factors for recent infection compared with the uninfected population.

Recent HIV infection was associated with having more than two sexual partners (as compared to none) (adjusted odds ratio 2.5, 95% confidence intervals 1.3 – 4.6), never using a condom with sex partners outside marriage (AOR 3.3) and being an uncircumcised man (AOR 2.5). Those positive for HSV-2, the virus that causes genital herpes, were 3.9 times more likely to have been recently infected.

The researchers calculated the population attributable risk of the various risk factors (the proportion of infections that could be attributed to different risk factors identified by the multivariate analysis) and found that 31% could be attributed to HSV-2 infection, and 20% to lack of circumcision. No other risk factors played such a prominent role; just 2.7% of recent infections could be attributed to lack of condom use with partners outside marriage, and 8% to the acquisition of a sexually transmitted infection.

Education level, employment status, age at first sex, syphilis, alcohol use and current pregnancy were not associated with an increased risk of recent HIV infection in this study.

Eight-four per cent of recent infections occurred in those who said they had had no sexual partners outside marriage in the previous year. A sub-study of 79 married, recently infected individuals whose partners had a known HIV status found that in 49% of cases the partner was HIV-negative, suggesting that this group had been less than frank about their sexual behaviour.

But in half of cases, the spouse was HIV-positive, and around a third of these spouses had themselves been recently infected.

Wolfgang Hladik said that up to 50% of new infections in Uganda could be prevented by promotion of male circumcision, monogamy and condom use outside marriage, and highlighted the need to promote HIV testing and counselling among married people.

In discussion after the presentation, Hladik admitted that the BED capture assay had the potential to over-estimate HIV incidence if it captured a substantial number of individuals in late-stage HIV infection, since these people might also register as positive on the assay. The only way to determine if the epidemic is beginning to expand is by carrying out further surveys to measure prevalence and incidence over time, he said.