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 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, based at Imperial College London.

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 housed within the Department of Infectious Disease Epidemiology, in the School of Public Health, Faculty of Medicine, at Imperial College London. It consists of the following members: 

  • Samir Bhatt, Lecturer
    Dr Sam Bhatt joined as a Lecturer in Geostatistics in the Department of Infectious Disease Epidemiology at Imperial College and works with UNAIDS Reference Group. His interests lie in the development and application of mathematical models to address policy-relevant questions about infectious diseases. Through his DPhil and subsequent postdoctoral research at Oxford University, he trained as a statistical geneticist investigating the evolutionary and ecological dynamics of RNA viruses. He has since moved to spatial modelling and mapping of major tropical diseases (malaria and dengue) and HIV.
  • Jeffrey Eaton, Senior Lecturer
    Dr Jeff Eaton is a Senior Lecturer within the Department of Infectious Disease Epidemiology. 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. 
  • Simon Gregson, co-chair
    Professor Simon Gregson is co-Principal Investigator of the UNAIDS Reference Group, as well as Director of the Manicaland HIV/STD Prevention Project in Zimbabwe. He is a Professor of Demography and Behavioural Science in the Department of Infectious Disease Epidemiology, in the School of Public Health at Imperial College London, and a Board Member of the Biomedical Research and Training Institute. His current research interests include the impact of the scale-up of anti-retroviral treatment on trends in the HIV epidemic, the demographic impact of HIV/AIDS, and measurement of the effectiveness of HIV control programmes - including combined interventions, community responses to HIV/AIDS, and conditional and unconditional cash transfers to improve the well-being and development of orphans and vulnerable children.
  • Timothy Hallett, co-chair
    Professor Tim Hallett is co-Principal Investigator of the UNAIDS Reference Group, as well as Director of the HIV Modelling Consortium. He is a Professor of Global Health based at the Department of Infectious Disease Epidemiology.  His work centres on the development and application of mathematical models for interpreting surveillance data, analyzing trials and planning interventions.The overall aim of his research is to come to conclusions about the optimal use of limited resources in response to the HIV epidemic worldwide. 
  • Sabrina Lamour, Project Manager
    Dr Sabrina Lamour joined UNAIDS Reference Group as a project manager in 2016, after obtaining her PhD in Clinical Medicine Research and a MRes in Biomedical Research, both at Imperial College London. She had obtained her degree in Biomedical Sciences from Durham University. Her research background had been focused on investigating host responses in tropical infectious diseases, particularly parasitic and viral infections, and has also included voluntary clinical work in southern Cote d’Ivoire. Prior to this, Sabrina was employed as  a Research Associate for UCB Pharma in immunology.
  • Tara Mangal, Research Associate
    Dr Tara Mangal's research interests focus on the epidemiology of HIV and the use of mathematical modelling and statistical analysis to understand disease transmission and develop control strategies. She is currently developing methods using routine surveillance data to estimate HIV incidence trends in settings with concentrated epidemics and estimating the impact of ART on mortality in Brazil. Prior to joining the group, she worked on assessing the impact of oral poliovirus vaccines and inactivated poliovirus vaccines on poliovirus transmission in endemic countries and developing models to inform policy decisions.
  • Katherine Wilson, Research Assistant
    Kate Wilson has been working in the Department of Infectious Disease Epidemiology as a research assistant for the UNAIDS Reference Group, since November 2015. She is investigating spatial patterns of antenatal care service use and HIV prevalence among pregnant women in sub-Saharan Africa. Prior to joining the group, she completed a Bachelor’s degree in Natural Sciences and a Master’s degree in Public Health Epidemiology.


Individual Technical Advisors and Research Partners

  • Le Bao, Pennsylvania State University, State College, Pennsylvania, USA
  • Giorgos Bakoyannis and Constantin Yiannoutsos,  IeDEA Network, Indiana University, Indianapolis, USA
  • Tim Brown, East-West Center, Honolulu, Hawaii, USA 
  • Txema Calleja, World Health Organization, Geneva, Swizerland
  • Pete Gething, Oxford University, Oxford, UK
  • James Hargreaves and Brian Rice, MeSH Consortium, London School of Hygiene and Tropical Medicine, London, UK
  • Leigh Johnson, University of Cape Town, Cape Town, South AfricA
  • John Stover, Avenir Health, Glastonbury, CT, USA
  • Basia Zaba and Emma Slaymaker, ALPHA Network, London School of Hygiene and Tropical Medicine, London, UK
  • Complete lists of all current and past members of Reference Group Meetings can be found in their respective Meeting Reports, available online under [Meetings]


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