A series of observational studies conducted by IAVI document extremely high HIV prevalence and incidence rates in some populations and surprisingly low ones in others. IAVI runs a project called the African HIV Prevention Partnership that conduct observational studies in different parts of Africa to uncover populations in particular need of prevention intervention. This is work preparatory to creating an African HIV Clinical Research and Prevention Trials Network similar to HPTN in the US.
Aidsmap reports that their paper looks at three prevalence and ten incidence studies in varied populations in the countries of Uganda, Rwanda, Kenya, Zambia and South Africa.
In the prevalence studies, a variety of populations in Uganda and Kenya were studied including rural communities, clinic attendees, a random whole-area population sample, and in Nairobi female sex workers (FSWs) and their clients. Groups in which there was particularly high HIV prevalence includes FSWs (20% – in their clients it was 7%), and divorced and widowed people (as opposed to single or married ones), where prevalence was 28% in a Kenyan study, and 22% in a Ugandan one. HIV was also more common in urban versus rural populations: it was 9% urban versus 2% rural people in a Kenyan study, and, in a Ugandan one, 16% versus 10% for people who lived near a highway versus people whose homes were only accessible by foot.
Peak prevalence age was 30-34 in two studies (16.5% in Uganda and 24% in FSWs) and in the non-FSW studies women had higher prevalence than men (in women, 10% and 13% in two studies versus, in men, 5% and 9%). Condom use, especially irregular use, was actually associated with higher HIV prevalence than not using them at all, but possibly because it was associated with casual sex. In Nairobi FSWs and clients, prevalence was 17.5% in condom users versus 10% in non-users. In Masaka, Uganda prevalence was 10% in people who never used condoms, and also in people who used them more than half the time: but it was 15% in people who used them only occasionally. Prevalence in people with one steady partner was lower (8-11% across studies) than in people who had more than one (14-17%). Genital ulcer disease (herpes, syphilis and the like – GUD) were associated with 2.5 to four times the prevalence than in people who did not have GUD.
But it was the incidence studies that found continuing high, and in some cases extraordinarily high, rates of ongoing HIV infection in some communities and groups – and low rates in seemingly similar ones.
One of the easiest and most important populations in which to conduct incidence is serodiscordant couples. In most but not all studies of serodiscordant couples annual HIV incidence was higher where the female partner was the initially HIV-negative one. Very high rates were observed in Lusaka, Zambia (9% a year in female partners, 7% in male) and Ndola in the same country (11% in women and 6% in men).
The "real-life" effect of placing the positive partner on ART was documented in one study in Masaka, Uganda where annual HIV incidence in serodiscordant couples was 4% in male partners and 5% in female but only 1% in partners of either gender when the HIV-positive partner was on ART. In the latter case particularly, much of this continued HIV infection may have come from outside the main relationship: IAVI genotyped all viruses in the HIV positive partners and found that from 20% to 33% of the infections in their studies came from someone other than the main partner, with one exception on Uganda where there were no "unlinked" infections.
Other groups in which very high incidence was found were MSM, with annual incidence rates of 7% and 6% at two places in Kenya and 9.5% at Rustenberg in South Africa; women in ‘peripheral communities', that is irregular housing in Rustenburg (9%) and members of fishing communities in Lake Victoria (10% in women in one Ugandan location and 5% in men).
And yet, at the same time, some groups with very high prevalence did not have a high rate of ongoing HIV infection. Even though HIV prevalence in Nairobi FSWs was high (see above), annual incidence was very low: in rural communities in Masaka where HIV prevalence was 10%, ongoing HIV incidence was so low in the general population that the team shifted their incidence survey to serodiscordant couples and fishing communities. And in one study in Kenya there were no infections observed within discordant couples at all (this study is unpublished so there is as yet no explanation for this).
One striking and near-universal finding was that enrolment into an HIV incidence study brought down incidence in itself. There were astoundingly high HIV incidence rates among some people in the first three months of their involvement in incidence studies: 15% and 19% in HIV-negative women in Zambian serodiscordant couples, 16% in Kenyan MSM, 12% among women with casual partners in South Africa. In all cases, although incidence remained high, it fell 1.5 to 4-fold after the first three months of being in the survey. This phenomenon has been seen in HIV prevention studies before and may be due to regular monitoring and the attention and counselling of healthcare workers.
HIV prevalence in sub-Saharan Africa has been in decline throughout the period of these studies and access to ART has expanded hugely. However what these two studies show is that the HIV epidemic is still very much an ongoing one in some groups in Africa.
[link url="http://www.aidsmap.com/No-improvements-in-CD4-count-at-diagnosis-in-African-patients-in-last-decade/page/2942452/"]Full Aidsmap report[/link]
[link url="http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0116100"]PLOS One article[/link]