Modes of Transmission Model

© UNAIDS 2010

To help optimize the allocation of resources in HIV prevention programmes, the UNAIDS/World Bank initiative ‘Know Your Epidemic – Know Your Response’ has been designed to facilitate programme managers to examine the sources of HIV infections in a country, which can then be used to guide prevention programme and data collection priorities.


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.


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.


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. 



HIV Modelling Consortium - Work Package 1

Request for funding applications

Funding issued

MC 1.1: PI Anna Foss - London School of Hygiene & Tropical Medicine

MC 1.2: PI Joshua Salomon - Harvard School of Public Health

MC 1.2: PIs Marie-Claude Boily & Sharmistha Mishra - Imperial College London

MC 1.3: PI Jan Hontelez - Erasmus Medical Centre

MC 1.3: PIs Marie-Claude Boily, Marc Brisson and Peter Vickerman - Imperial College London, Universite Laval, London School of Hygiene & Tropical Medicine