Supervisory team
LSHTM
- Lead supervisor: James Hargreaves ([email protected])
Nagasaki University
- Supervisor: Su Myat Han ([email protected])
- Supervisor: Hiromu Ito ([email protected])
- Supervisor: Michiko Toizumi ([email protected])
Dr Liz Fearon at University College London (UCL) and Primrose Matambanadzo from the Centre for Sexual Health and HIV/AIDS Research (CeSHHAR) Zimbabwe will join as Co-supervisor and Advisor.
Dr Fuminari Miura, joint Nagasaki University and National Institute for Public Health and the Environment (RIVM, Netherlands), will also be a Nagasaki University Co-supervisor.
Project
Female sex workers are disproportionately affected by HIV in Africa, with estimated HIV incidence 8 times higher than among matched total population women (1). To meet their health needs and to reduce population transmission, sex workers are recognised as a priority population by UNAIDS, WHO, and many country strategies.
Foundational to our understanding of STI population transmission dynamics is the large variance in the number of sexual partners across the population, without which sexually transmitted infections (STIs) could not persist given low mean partner numbers. It follows that sex workers are disproportionately affected by STIs and play an important role in transmission among the population as a whole.
However, sex work varies considerably within and across different settings: in terms of its organisation (self-led, venue-based hierarchies); legal status; setting (street or bar/club-based, brothel or home-based; online advertising); intensity in terms of client numbers and in relationships with clients. These, differences mean that the structure and composition of sex work networks likely vary also in terms of key network characteristics understood to affect transmission. Furthermore, sex workers themselves do not have equal ability to access or engage with HIV prevention, which could interact with network position in influencing the effectiveness of targeting prevention among this population.
Few recent studies have modelled the characteristics of sex work partnership networks in detail (2) to explore how network structure might influence targeting of HIV prevention among sex workers in the current epidemic phase.
This PhD project aims to use a dynamic bipartite network modelling framework to explore how characteristics of a heterosexual sex work network, such as degree distribution (distribution of sexual partner numbers), degree assortativity (tendency for high partner sex workers to have high partner clients), time and location-based clustering of contacts influence transmission of HIV and optimal prevention distribution. The PhD will focus on Zimbabwe, where sex workers remain affected by high HIV incidence and which has had a research-informed sex work programme since 2009, including more than 40 respondent driven sampling surveys, and a sex worker coital diary study. Benefitting from a 2026-2030 study investigating equity patterns in infectious disease prevention in Africa (PI Hargreaves, Co-Is Matambadnadzo and Fearon), the PhD will explore data consistent network structure and distribution of new long-acting forms of injectable HIV pre-exposure prophylaxis.
Using this foundational model informed by Zimbabwe data, we will conduct model-based comparison of sex work-associated transmission dynamics with other settings such as Japan, building on Dr Ito’s work to analyse online sex work networks (3).
Research questions
- What are key network characteristics that describe the sex work network in Zimbabwe?
- What associations can be observed between network position and access to/engagement with HIV prevention and treatment, and engagement with the sex workers programme, in models consistent with reported data?
- Given network position and gaps in prevention coverage, how should limited HIV prevention resources be targeted to maximise prevention benefit and equity?
- How might transmission patterns, and prevention targeting, differ for a setting in which sex work network structure is different?
References
1. Jones, H.S. et al , HIV incidence among women engaging in sex work in sub-Saharan Africa: a systematic review and meta-analysis. Lancet Global Health. 2024 Aug;12(8):e1244-e1260. doi: 10.1016/S2214-109X(24)00227-4
2. Mulberry N., et al. HIV control strategies for sex worker-client contact networks. J R Soc Interface. 2019 Sep 27;16(158):20190497. doi: 10.1098/rsif.2019.0497.
3. Ito H, Shigeta K, Yamamoto T, Morita S. Exploring sexual contact networks by analyzing a nationwide commercial-sex review website. PLoS One. 2022 Nov 3;17(11):e0276981. doi: 10.1371/journal.pone.0276981.
The role of LSHTM and NU in this collaborative project
This project aims to bring together expertise in infectious disease modelling, network science, HIV epidemiology and programme implementation with sex workers, which exists across LSHTM and partners and Nagasaki University.
In this collaboration, the LSHTM supervisor, Prof Hargreaves, along with CeSHHAR Advisor Ms Matambanadzo, and co-supervisor Dr Fearon (UCL), will bring expertise in HIV and STI prevention and treatment programmes for sex workers in Zimbabwe and the region, along with an applied lens on the implications of population dynamics understanding for public health practice. Prof Hargreaves and CeSHHAR have collaborated since 2011 in epidemiological and implementation science research to support the Sisters with a Voice Zimbabwe sex workers programme. The project will also benefit from its relationship to the “Breaking the inverse laws”: Accelerating the health equity impact of prevention and control interventions for infectious diseases in Africa project, a Wellcome Trust funded 2026-2030 research programme to investigate the prevention or mitigation of inequalities in benefit from new infectious disease technologies in Africa, for which Prof Hargreaves is a lead, co-led by Ms Matambanadzo and Dr Fearon.
The Nagasaki team brings expertise, skills and experience in network analysis (Dr Han and Dr Ito) and infectious disease modelling ((Dr Han and Dr Miura). The Nagasaki supervisors will support the student in adapting the network model to explore other types of sex work networks informed via literature review and via engagement with Dr Ito’s work on online sex work networks in Japan and internationally. This will enable exploration of different sex work network structures affecting transmission and in assessing the generalizability of the findings, with the aim of proposing more tailored preventive measures for different settings.
Particular prior educational requirements for a student undertaking this project
- Essential: Masters qualification in epidemiology or infectious diseases in population health, medical statistics or public health data science, programming experience in R, Python or another language or, if a more quantitative academic qualification (e.g. applied mathematics, engineering, physics), then some experience/demonstrated interest in epidemiological modelling or public health.
- Desirable: experience in epidemic modelling, network science, programming, data analysis or HIV, STI and/or sex work research. Experience working in or conducting research in Southern Africa.
Skills we expect a student to develop/acquire whilst pursuing this project
- Dynamic network modelling skills
- Programming and good programming practice skills
- Exposure to applying disease dynamics
- Understanding to public health implications
- Stakeholder engagement
- Communication of modelling