Characterizing HIV prevalence distribution across sub-populations at variable levels of sexual behavior

A review of interprovincial variations in HIV prevalence rates in Zimbabwe

Despite the proven remarkable decline of HIV prevalence in the sub-Saharan Africa region, both sub-regional and within-country disparities in HIV prevalence persist. This paper is a survey of literature on HIV prevalence and spread in Zimbabwe, focusing on provincial differences within the national picture of a decline in new infections. In particular, it raises the question of why prevalence and infection rates seem to be disproportionately higher in Matabeleland relative to other provinces of the country. This disparity cannot be adequately explained on the basis of national behavioural analyses as has been the case. The paper suggests possible additional nuances in the forms of analysis and proposes a change of focus in HIV-prevention strategies from national level to provincial considerations of the multiple factors influencing variations in HIV infection rates at provincial level. Using the different contextual conditions between provinces as a way to examine what might be the additional significant variables, the paper brings variations that go beyond sexual behaviour.

Investigating Voluntary Medical Male Circumcision Program Efficiency Gains through Subpopulation Prioritization: Insights from Application to Zambia

Background

Countries in sub-Saharan Africa are scaling-up voluntary male medical circumcision (VMMC) as an HIV intervention. Emerging challenges in these programs call for increased focus on program efficiency (optimizing program impact while minimizing cost). A novel analytic approach was developed to determine how subpopulation prioritization can increase program efficiency using an illustrative application for Zambia.

Methods and Findings

A population-level mathematical model was constructed describing the heterosexual HIV epidemic and impact of VMMC programs (age-structured mathematical (ASM) model). The model stratified the population according to sex, circumcision status, age group, sexual-risk behavior, HIV status, and stage of infection. A three-level conceptual framework was also developed to determine maximum epidemic impact and program efficiency through subpopulation prioritization, based on age, geography, and risk profile. In the baseline scenario, achieving 80% VMMC coverage by 2017 among males 15–49 year old, 12 VMMCs were needed per HIV infection averted (effectiveness). The cost per infection averted (cost-effectiveness) was USD $1,089 and 306,000 infections were averted. Through age-group prioritization, effectiveness ranged from 11 (20–24 age-group) to 36 (45–49 age-group); cost-effectiveness ranged from $888 (20–24 age-group) to $3,300 (45–49 age-group). Circumcising 10–14, 15–19, or 20–24 year old achieved the largest incidence rate reduction; prioritizing 15–24, 15–29, or 15–34 year old achieved the greatest program efficiency. Through geographic prioritization, effectiveness ranged from 9–12. Prioritizing Lusaka achieved the highest effectiveness. Through risk-group prioritization, prioritizing the highest risk group achieved the highest effectiveness, with only one VMMC needed per infection averted; the lowest risk group required 80 times more VMMCs.

Conclusion

Epidemic impact and efficiency of VMMC programs can be improved by prioritizing young males (sexually active or just before sexual debut), geographic areas with higher HIV prevalence than the national, and high sexual-risk groups.

Spatial variability in HIV prevalence declines in several countries in sub-Saharan Africa

Evidence suggests substantial declines in HIV prevalence in parts of sub-Saharan Africa. However, the observed aggregate declines at the national level may obscure local variations in the temporal dynamics of the infection. Using spatial scan statistics, we identified marked spatial variability in the within-country declines in HIV prevalence in Tanzania, Malawi, Kenya, and Zimbabwe. Our study suggests that the declines in the national HIV prevalence in some of the SSA countries may not be representative of downward trends in prevalence in areas of high HIV prevalence, as much as the result of sharp declines in prevalence in areas of already low HIV prevalence. Our findings provide insights for resource allocation and HIV prevention interventions in these countries.