Modes of Transmission Model

Background

The method for estimating sources of infection is the ‘Modes of Transmission’ model, a spreadsheet-based tool that uses inputs on the numbers of individuals in particular risk groups (sex workers, clients of sex workers, those with casual partnerships, etc.), HIV prevalence and behaviours among the groups and transmission risk associated with the behaviours to project the number of new infections in each group in the next year. It is one of the most frequently used tools across the world to inform HIV prevention programmes. To allocate resources in this way requires knowledge of HIV incidence in different populations, which is difficult to obtain in the field. As such mathematical modelling presents an alternative.

As of 2012, over 40 countries had completed or begun an MoT analysis.  A formal evaluation on the impact of the MoT on HIV prevention budget allocation has not been performed.  Concerns have been raised regarding the quality of the model outputs as well as limitations related to the data needs and interpretation of results. Considering the importance of the question and the far-reaching impact of this model, the HIV Modelling Consortium undertook the task of evaluating it.

Approach

A meeting was held in April 2011 gathering modellers, demographers and epidemiologists familiar with the MoT to present work on the model and discuss its limitations. Following this, the Consortium commissioned a number of research projects (see RFAs listed on the right hand side of the page) to further explore some of the key issues raised during the meeting with a vision to update or revise the model in the near future.

Outcomes

The commissioned work has reached its final phase of completion and the findings and insights obtained have been summarized and reviewed by all of the groups involved (see references listed below). Further to the recommendations from the research groups, the HIV Modelling Consortium Secretariat has begun to develop a proposal for a revised model that takes into consideration data constraints and programmatic needs. 

Resources

• For further reading on this project, please see the review article by Kelsey Case et al. on behalf of the HIV Modelling Consortium published in the November 2012 World Health Organization Bulletin: http://www.who.int/bulletin/volumes/90/11/12-102574.pdf
• Prudden HJ, Watts CH, Vickerman P, Bobrova N, Heise L, Ogungbemi MK, Momah A, Blanchard JF, Foss AM. 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. AIDS. 27(16):2623-2635, October 23, 2013: 10.1097/01.aids.0000432476.22616.2f
• Shubber Z, Mishra S, Vesga J, Boily MC. The HIV Modes of Transmission Model: a systematic review of its findings and adherence to guidelines. Sex Transm Infect 2013;89: A52: http://sti.bmj.com/content/89/Suppl_1/A52.1.full.pdf+html
• Sharmistha Mishra^, Michael Pickles, James Blanchard, Stephen Moses, Marie-Claude Boily. Distinguishing sources of HIV transmission from the distribution of newly acquired HIV infections: why is it important for HIV prevention planning? Sex Transm Infect: http://sti.bmj.com/content/90/1/19.full.pdf+html
• The code for the Incidence Patterns Model model can be found at the following link: https://www.dropbox.com/sh/7unlpmd9vlecm1t/AACEf2lkcPTMeKNZhnm_ciURa?dl=0 

HIV Modelling Consortium - Work Package 1