Can the UNAIDS Modes of Transmission Model be Improved?: A Comparison of the Original and Revised Model Projections using Data from a Setting in West Africa

November 2013 - Structural Prevention

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Prudden, H.J., Watts, C.H., Vickerman, P., et al. AIDS (October 2013), Vol. 27 No. 16, pp. 2623-2635.

The Modes of Transmission Model (MoT), developed by the Joint United Nations Program on HIV/AIDS (UNAIDS), uses the HIV prevalence and behavioral patterns of subpopulations to estimate the distribution of HIV infections. The authors acknowledged the benefits of the model's simplicity, but called for its revision on the grounds that the current MoT may provide misleading estimates, particularly in settings with key differences in subpopulations. The authors compared current MoT projections for Cross River state in Nigeria (2009) with a revised MoT projection that more explicitly defined heterogeneous subgroups and used updated parameters. In the revised MoT projection, "female sex workers (FSWs)" are recategorized as "brothel-based," "non-brothel-based," and "engaging in transactional sex," and "discordant couples" are disaggregated from the category "low-risk group." While the original analysis showed most new HIV infections (73 percent) occurring through heterosexual sex in the general population, the revised model revealed a higher burden (34 percent) among discordant couples. The revised model also indicated significantly more infections among key populations compared to the original MoT (45 versus 21 percent), and showed that brothel-based FSWs and women involved in transactional sex contribute most of the HIV infections that occur within key populations. These results emphasize the importance of identifying high-risk subpopulations to provide them effective prevention options.

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