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HIV epidemic appraisals for assisting in the design of effective prevention programmes: shifting the paradigm back to basics - PubMed

HIV epidemic appraisals for assisting in the design of effective prevention programmes: shifting the paradigm back to basics

Sharmistha Mishra et al. PLoS One. 2012.

Abstract

Background: To design HIV prevention programmes, it is critical to understand the temporal and geographic aspects of the local epidemic and to address the key behaviours that drive HIV transmission. Two methods have been developed to appraise HIV epidemics and guide prevention strategies. The numerical proxy method classifies epidemics based on current HIV prevalence thresholds. The Modes of Transmission (MOT) model estimates the distribution of incidence over one year among risk-groups. Both methods focus on the current state of an epidemic and provide short-term metrics which may not capture the epidemiologic drivers. Through a detailed analysis of country and sub-national data, we explore the limitations of the two traditional methods and propose an alternative approach.

Methods and findings: We compared outputs of the traditional methods in five countries for which results were published, and applied the numeric and MOT model to India and six districts within India. We discovered three limitations of the current methods for epidemic appraisal: (1) their results failed to identify the key behaviours that drive the epidemic; (2) they were difficult to apply to local epidemics with heterogeneity across district-level administrative units; and (3) the MOT model was highly sensitive to input parameters, many of which required extraction from non-regional sources. We developed an alternative decision-tree framework for HIV epidemic appraisals, based on a qualitative understanding of epidemiologic drivers, and demonstrated its applicability in India. The alternative framework offered a logical algorithm to characterize epidemics; it required minimal but key data.

Conclusions: Traditional appraisals that utilize the distribution of prevalent and incident HIV infections in the short-term could misguide prevention priorities and potentially impede efforts to halt the trajectory of the HIV epidemic. An approach that characterizes local transmission dynamics provides a potentially more effective tool with which policy makers can design intervention programmes.

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Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Figure 1
Figure 1. Epidemic typologies based on an alternative framework.

High-risk groups (pink box) comprise of female sex workers, high-risk men who have sex with men, and injection drug users. Yellow circles indicate direct sexual partners of members of a high-risk group (for example, male clients). Grey boxes comprise the remainder of the general population. Red lines delineate sexual partnerships that contribute to emergence and persistence of HIV in the local community (epidemiologic drivers), such that in the absence of these partnerships, the epidemic would fail to establish.

Figure 2
Figure 2. A proposed approach for assigning HIV epidemic typologies for the design of HIV prevention programmes.

The epidemic drivers of concentrated epidemics are networks of HRGs, whereas multiple partnerships enables HIV to be sustained in the generalizing epidemic. In the mixed epidemic, there is substantial contribution from both the HRGs and the general population in sustaining HIV transmission. Int refers to intermediate.

Figure 3
Figure 3. Modes of Transmission sensitivity analysis with various tiers of data-sources for Belgaum, India.

FTFI, face to face interview; HRG, high-risk group; PBS, polling booth survey. Indirect client estimate was based on reported client volume by rural and urban female sex workers. Redistribution in incident infections is driven predominantly by the estimate of the client population (3.0 to 16.8%) and multiple partnerships (3.1 and 0.8% among males and females respectively using state-level estimates and 9.9 and 1.5% among males and females respectively using PBS estimates). Increasing the population size of each of these risk groups resulted in a predominance of infections among direct partners of clients and persons engaged in multiple partnerships.

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