Over the past decade, there has been a massive scale-up of primary and secondary prevention services to reduce the population-wide incidence of HIV. However, the impact of these services on HIV incidence has not been demonstrated using a prospectively followed, population-based cohort from South Africa—the country with the world’s highest rate of new infections. To quantify HIV incidence trends in a hyperendemic population, we tested a cohort of 22,239 uninfected participants over 92,877 person-years of observation. We report a 43% decline in the overall incidence rate between 2012 and 2017, from 4.0 to 2.3 seroconversion events per 100 person-years. Men experienced an earlier and larger incidence decline than women (59% vs. 37% reduction), which is consistent with male circumcision scale-up and higher levels of female antiretroviral therapy coverage. Additional efforts are needed to get more men onto consistent, suppressive treatment so that new HIV infections can be reduced among women.

Existing public health systems fail to properly account for migration, and actionable knowledge of the health requirements of migrants is still lacking. A large body of research has shown that migrants are more likely to enter into the healthcare system late and are less likely to be retained at successive stages of the HIV treatment cascade. HIV-infected migrants are especially vulnerable to a wide range of social, economic and political factors that include a lack of direct access to healthcare services; exposure to difficult or oppressive work environments; the separation from family, friends and a familiar sociocultural environment. Realizing the full treatment and preventive benefits of the UNAIDS 90-90-90 strategy will require reaching all marginalized subpopulations of which migrants are a particularly large and important group.

Objective:To quantify the space-time dimensions of human mobility in relationship to the risk of HIV acquisition.Methods:We used data from the population cohort located in a high HIV prevalence, rural population in KwaZulu-Natal, South Africa (2000–2014). We geolocated 8006 migration events (representing 1 028 782 km traveled) for 17 743 individuals (≥15 years of age) who were HIV negative at baseline and followed up these individuals for HIV acquisition (70 395 person-years). Based on the complete geolocated residential history of every individual in this cohort, we constructed two detailed time-varying migration indices. We then used interval-censored Cox proportional hazards models to quantify the relationship between the migration indices and the risk of HIV acquisition.Results:In total, 17.4% of participants migrated at least once outside the rural study community during the period of observation (median migration distance = 107.1 km, interquartile range 18.9–387.5). The two migration indices were highly predictive of hazard of HIV acquisition (P < 0.01) in both men and women. Holding other factors equal, the risk of acquiring HIV infection increased by 50% for migration distances of 40 km (men) and 109 km (women). HIV acquisition risk also increased by 50% when participants spent 44% (men) and 90% (women) of their respective time outside the rural study community.Conclusion:This in-depth analysis of a population cohort in a rural sub-Saharan African population has revealed a clear nonlinear relationship between distance migrated and HIV acquisition. Our findings show that even relatively short-distance migration events confer substantial additional risk of acquisition.

HIV/AIDS-related stigma threatens to undermine interventions to prevent and treat HIV/AIDS. To address stigma in a South African community, a thorough understanding of the nature of stigma in the specific cultural context is needed. The goals of this research were to assess the level of stigmatising attitudes among members of a community, compare this to the level of stigma that is perceived to exist within the community and determine to what extent stigmatising attitudes are affected by socio-demographic characteristics, HIV-related experience and cultural beliefs. A questionnaire was completed by 1077 respondents in key areas in two communities in Tshwane, South Africa. The questionnaire included an assessment of HIV-related experience, HIV-knowledge, personal stigma and perceptions of stigma within the community. The findings indicate that the level of personal stigma was significantly lower than that perceived to be present in the community. Respondents who were more stigmatising were older, male, less educated, and less knowledgeable about HIV. They were less likely to know someone with HIV and had more traditional cultural viewpoints. While socio-demographic and cultural factors are difficult to change, efforts aimed at increasing people’s knowledge and experience of the epidemic occurring in their community could change the level of stigmatising attitudes within their community. Such efforts could have potential benefits in addressing the epidemic and providing greater support for those with HIV.

Objective:To quantify the contribution of specific sexual partner age groups to the risk of HIV acquisition in men and women in a hyperendemic region of South Africa.Design:We conducted a population-based cohort study among women (15–49 years of age) and men (15–55 years of age) between 2004 and 2015 in KwaZulu-Natal, South Africa.Methods:Generalized additive models were used to estimate smoothed HIV incidence rates across partnership age pairings in men and women. Cox proportional hazards regression was used to estimate the relative risk of HIV acquisition by partner age group.Results:A total of 882 HIV seroconversions were observed in 15 935 person-years for women, incidence rate = 5.5 per 100 person-years [95% confidence interval (CI), 5.2–5.9] and 270 HIV seroconversions were observed in 9372 person-years for men, incidence rate = 2.9 per 100 person-years (95% CI, 2.6–3.2). HIV incidence was highest among 15–24-year-old women reporting partnerships with 30–34-year-old men, incidence rate = 9.7 per 100 person-years (95% CI, 7.2–13.1). Risk of HIV acquisition in women was associated with male partners aged 25–29 years (adjusted hazard ratio; aHR = 1.44, 95% CI, 1.02–2.04) and 30–34 years (aHR = 1.50, 95% CI, 1.08–2.09) relative to male partners aged 35 and above. Risk of HIV acquisition in men was associated with 25–29-year-old (aHR = 1.72, 95% CI, 1.02–2.90) and 30–34-year-old women (aHR = 2.12, 95% CI, 1.03–4.39) compared to partnerships with women aged 15–19 years.Conclusion:Age of sexual partner is a major risk factor for HIV acquisition in both men and women, independent of one's own age. Partner age pairings play a critical role in driving the cycle of HIV transmission.

BackgroundIt is common to use the mid-point between the latest-negative and earliest-positive test dates as the date of the infection event. However, the accuracy of the mid-point method has yet to be systematically quantified for incidence studies once participants start to miss their scheduled test dates.MethodsWe used a simulation-based approach to generate an infectious disease epidemic for an incidence cohort with a high (80–100%), moderate (60–79.9%), low (40–59.9%) and poor (30–39.9%) testing rate. Next, we imputed a mid-point and random-point value between the participant’s latest-negative and earliest-positive test dates. We then compared the incidence rate derived from these imputed values with the true incidence rate generated from the simulation model.ResultsThe mid-point incidence rate estimates erroneously declined towards the end of the observation period once the testing rate dropped below 80%. This decline was in error of approximately 9%, 27% and 41% for a moderate, low and poor testing rate, respectively. The random-point method did not introduce any systematic bias in the incidence rate estimate, even for testing rates as low as 30%.ConclusionsThe mid-point assumption of the infection date is unjustified and should not be used to calculate the incidence rate once participants start to miss the scheduled test dates. Under these conditions, we show an artefactual decline in the incidence rate towards the end of the observation period. Alternatively, the single random-point method is straightforward to implement and produces estimates very close to the true incidence rate.

Monitoring HIV population viral load (PVL) has been advocated as an important means of inferring HIV transmission potential and predicting the future rate of new HIV infections in a particular community. However, the relationship between the PVL measures and directlymeasured HIV incidence has not been quantified in any setting and most importantly not in a hyper-endemic sub-Saharan African setting. We assessed this relationship using one of Africa's largest population-based prospective population cohorts, in rural KwaZulu-Natal, South Africa in which we followed 8,732 HIV-uninfected participants between 2011 and 2015. Despite clear evidence of spatial clustering of high viral loads in some communities, our results demonstrate that PVL metrics that are derived from aggregation of viral load data only from the HIV-positive members of a particular community did not predict HIV incidence in this typical hyper-endemic, rural African population. Only once we used modified PVL measures which combined viral load information with the underlying spatial variation in the proportion of the population infected (HIV prevalence) did we find a consistently strong relationship with future risk of HIV acquisition. For example, every 1% increase in the overall proportion of a population having a detectable virus, was independently associated with a 6.3% increase in the risk of HIV acquisition (p=0.001). In hyper-endemic African populations, these modified PVL indices could play a key role in targeting and monitoring interventions in the most vulnerable communities where the future rate of new HIV infections is likely to be highest.

SummaryBackgroundStudies of HIV-serodiscordant couples in stable sexual relationships have provided convincing evidence that antiretroviral therapy can prevent the transmission of HIV. We aimed to quantify the preventive effect of a public-sector HIV treatment and care programme based in a community with poor knowledge and disclosure of HIV status, frequent migration, late marriage, and multiple partnerships. Specifically, we assessed whether an individual's hazard of HIV acquisition was associated with antiretroviral therapy coverage among household members of the opposite sex.MethodsIn this prospective cohort study, we linked patients' records from a public-sector HIV treatment programme in rural KwaZulu-Natal, South Africa, with population-based HIV surveillance data collected between 2004 and 2012. We used information about coresidence to construct estimates of HIV prevalence and antiretroviral therapy coverage for each household. We then regressed the time to HIV seroconversion for 14 505 individuals, who were HIV-uninfected at baseline and individually followed up over time regarding their HIV status, on opposite-sex household antiretroviral therapy coverage, controlling for household HIV prevalence and a range of other potential confounders.Findings2037 individual HIV seroconversions were recorded during 54 845 person-years of follow-up. For each increase of ten percentage points in opposite-sex household antiretroviral therapy coverage, the HIV acquisition hazard was reduced by 6% (95% CI 2–9), after controlling for other factors. This effect size translates into large reductions in HIV acquisition hazards when household antiretroviral therapy coverage is substantially increased. For example, an increase of 50 percentage points in household antiretroviral therapy coverage (eg, from 20% to 70%) reduced the hazard of HIV acquisition by 26% (95% CI 9–39).InterpretationOur findings provide further evidence that antiretroviral therapy significantly reduces the risk of onward transmission of HIV in a real-world setting in sub-Saharan Africa. Awareness that antiretroviral therapy can prevent transmission to coresident sexual partners could be a powerful motivator for HIV testing and antiretroviral treatment uptake, retention, and adherence.FundingWellcome Trust and National Institute of Child Health and Human Development (US National Institutes of Health).