About Us

Who We Are

Mathematical methods developed with the guidance of the Reference Group on Estimates, Modelling and Projections are used by United Nations Joint Programme on HIV/AIDS (UNAIDS) to generate HIV estimates (available at AIDSinfo) for nearly every country in the world. These estimates have been critical for describing the nature and scale of HIV epidemics around the world.  Having these tools available provides countries with the essential information required to design effective and strategic programmes and efficiently plan for resource allocation. The Reference Group acts as an ‘open cohort’ of epidemiologists, demographers, statisticians, and public health experts. It is able to provide timely advice and also address ongoing concerns through both ad hoc and regular meetings. The group is co-ordinated by a Secretariat, managed at Imperial College London.
Lists of past members of Reference Group Meetings can be found in the meeting reports of all our [Meetings]

Our Mission 

Please see [Our Work ] page for further information on the history of the  Reference Group and our objectives. 

Secretariat Members

The Secretariat is managed at Imperial College London (within the Department of Infectious Disease Epidemiology, School of Public Health), UK, and the University of Cape Town (in the Centre for Infectious Disease Epidemiology and Research), South Africa. It is comprised of the following members: 

  • Jeffrey Eaton, Co-Chair
    Dr Jeff Eaton is a senior lecturer in HIV epidemiology within the Department of Infectious Disease Epidemiology at Imperial College. His research involves using mathematical models and statistical analysis to understand HIV epidemics in southern Africa and the potential impacts of HIV prevention strategies. His main research interests include understanding the epidemiological impacts of antiretroviral therapy on HIV epidemics in sub-Saharan Africa, improving methods and surveillance data for estimates of HIV trends, developing and validating mathematical models used to inform HIV policy decisions in generalized epidemic settings, HIV in children and adolescents in southern Africa, and data collection, analysis, and modelling of general-population HIV cohort studies. He holds a PhD in Infectious Disease Epidemiology from Imperial College London, and Master's degree in Statistics from the University of Washington. He has worked at demographic surveillance sites: the Agincourt Health and Population Unit in rural north-eastern South Africa and the Mekong Integrated Population Registration Areas of Cambodia (MIPRAoC). He collaborates extensively with the Manicaland HIV/STD Projection, a population-based HIV cohort in eastern Zimbabwe, and contributes to the UNAIDS Reference Group on Estimates, Modelling, and Projections and the Economics and Modelling working group of the HPTN 071 (PopART) community randomised trial of a combined HIV prevention package including test-and-treat.
  • Leigh Johnson Co-Chair
    Dr Leigh Johnson is a senior researcher at the Centre for Infectious Disease Epidemiology and Research, at the University of Cape Town, South Africa. His research interests are in HIV epidemiology and HIV modelling. He is also involved in a number of other disease modelling projects focusing on other sexually transmitted infections, cervical cancer, diabetes and tuberculosis. His modelling work has focused particularly on the South African context, and he is the lead developer of the Thembisa model, which is a widely used source of HIV and demographic statistics in South Africa. He serves on the editorial boards of ‘AIDS’ and ‘Infectious Disease Modelling’. He is also a member of the International epidemiology Databases to Evaluate AIDS (IeDEA) network.
  • Joshua Salomon, Co-Chair
    Professor Josh Salomon is a Professor of Medicine and a core faculty member in the Center for Health Policy and the Center for Primary Care and Outcomes Research. His research focuses on priority-setting in global health, within three main substantive areas: (1) measurement and valuation of health outcomes; (2) modeling patterns and trends in major causes of global mortality and disease burden; and (3) evaluation of health interventions and policies. Dr. Salomon is an investigator on projects funded by the Centers for Disease Control, National Institutes of Health and the Bill & Melinda Gates Foundation, relating to modeling of infectious and chronic diseases and associated intervention strategies; methods for economic evaluation of public health programs; measurement of the global burden of disease; and assessment of the potential impact and cost effectiveness of new health technologies. He is Director of the Prevention Policy Modeling Lab, which is a multi-institution research consortium that conducts health and economic modeling relating to infectious disease. Prior to joining the Stanford faculty, Prof. Salomon was Professor of Global Health at Harvard T.H. Chan School of Public Health.
  • Oli Stevens, Research Manager
    Oli Stevens joined the UNAIDS Reference Group as a research manager in 2018 in the Department of Infectious Disease Epidemiology at Imperial College London. His research focuses on understanding the epidemiology of the HIV epidemic in Mozambique and the development of mathematical models to capture fertility and antenatal care seeking dynamics. He holds Master's degrees in Public Health from the London School of Hygeine and Tropical Medicine and in Molecular Biochemistry from the University of Oxford.

Partnering Organisations


Our Funding

The Reference Group work closely with UNAIDS, who fund the Reference Group Secretariat through a grant to Imperial College London. For further information on UNAIDS, please visit www.unaids.org