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This thesis aims to describe the uptake and coverage of HIV testing and counselling (HTC) services in a community cohort study in rural Tanzania between 2003 and 2010, and to investigate the impact of HTC on changes in sexual risk behaviour and HIV incidence. Paper A uses data from three HTC services (community outreach HTC (CO-HTC), walk-in HTC (WI-HTC) and antenatal HTC) linked to the community cohort data to compare the characteristics of services users, and found that while WI-HTC was most likely attract HIV-positive individuals, the overall proportion of infected persons diagnosed was greatest at CO-HTC. Rates of repeat testing are important to understand given potential HIV treatment as prevention approaches. Paper B found that small proportions of cohort participants repeat tested between 2003 and 2010, although this improved over time. Paper C presents a quantitative analysis of the impact of CO-HTC on changes in sexual behaviour and HIV incidence, and found moderate associations between HTC use and reductions in some risk behaviours among HIV-negative participants, but no impacts among HIV-positive individuals or reductions in HIV incidence, possibly as a result of small sample sizes and a declining background incidence in the study area. Paper D presents findings from a qualitative study exploring the effectiveness of HIV prevention counselling messages, which showed that relationship dynamics constrained the extent to which HIV-negative women felt able to control their HIVrelated risk, and imbalanced client-counsellor interactions limited communication during counselling sessions. Overall, the findings from the thesis reveal that provision of different HTC models increased the uptake of services, but the proportions of individuals repeat testing were low and there was limited evidence for an impact of HTC on sexual risk reduction. Future research should explore the effectiveness of different HTC modalities in encouraging repeat testing among high risk HIV-negative individuals, influencing sexual behaviour change and linking HIV-positive people to care and treatment.

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Introduction: Mathematical models of HIV transmission have played an important role in helping to understand the drivers of the HIV epidemic, and shape the global HIV response. The underlying approaches, assumptions and structures used in HIV modelling have the potential to fundamentally influence the conclusions of any modelling analyses. For this reason, it is important that approaches to modelling HIV transmission in different contexts carefully consider how best to ‘characterise’ a populations distribution of risk and networks of sexual interaction based on data, and the implications of incorporating different levels of epidemiological complexity into their modelling. Across West Africa there are substantial variations in population HIV prevalence - ranging from 0.5-6%. To date, there has been limited exploration of the potential factors influencing this population variation. This PhD aims to inform our understanding of the determinants of population variations in HIV prevalence across West Africa, using a combination of ecological analysis of population data, and both simple and more complex epidemiological modelling. The findings are used both to explore the determinants of HIV transmission across West Africa, and to discuss the implications for future modelling and epidemic appraisal approaches. Methods: A range of modelling and epidemiological analytical approaches were used. Firstly, an existing policy model, The Modes of Transmission (MoT) model, designed to predict patterns of HIV incidence, was revised and re-parameterised using data from Nigeria, to explore the effect on overall conclusions of adding additional heterogeneity into the model, and considering more explicitly how to model HIV risk amongst lower-risk subgroups. Secondly, population data from 13 West African countries were compiled. Linear regression analyses were used to assess potential relationships between HIV prevalence in high-risk groups and population HIV prevalence and the size of high-risk population subgroups and HIV prevalence in the general population. Based on the findings from the MoT and ecological analysis, a dynamic deterministic model was developed to explore the variations in HIV prevalence across West Africa. The population model not only included sex work, client and general population sub-groups, but also included a category of adolescent females (15-24) and a category of males with multiple sexual partners, with a mixing formulation being used to vary the degree the adolescent females form partnerships with clients of female sex workers and the subgroup of males who have multiple partnerships Input parameters were sampled from ranges relevant for West Africa, using Latin Hypercube sampling. The model was fitted to equilibrium prevalence in the general population. Results: A critique and revisions to the MoT, identified high levels of infections in previously unrecognised subgroups. These included 16% of new infections occurring in young females engaging in transactional sex. Findings from the ecological analysis, showed that across West Africa HIV prevalence in FSWs and their clients is not associated with higher HIV prevalence in the general population. Instead, the size of groups of males and females with multiple partners is correlated with higher HIV prevalence levels. The deterministic model generated 11000 fits. Grouping fits, based on epidemic size (with 1% incremental increases from 0-6%), the findings revealed that population sizes of key subgroups is the predominant driver of the epidemic. For epidemics where prevalence is less than 3%, FSW population size is the most important determinant of HIV prevalence. For epidemics above 3%, it is the size of the group of adolescent females with multiple partners and their level of interaction with clients of FSWs that is the most significant variable related to higher HIV prevalence. When the limiting effects on HIV transmission of male circumcision are removed from the model, the findings are less clear, with both sex work and the role of adolescent females with multiple partners being important determinants of the epidemic. Circumcision is however shown to significantly limit the magnitude of an epidemic and epidemic categorisation should account for these variations accordingly. Conclusions: Behavioural heterogeneity has long been recognised as an important component of model development. The results from this thesis show the importance of carefully considering how to compartmentalise population HIV models. Even for simple static models, the inclusion of additional subgroups change model conclusions and suggests different intervention priorities. The use of results and findings from ecological analyses, whilst unable to provide strong evidence of causality, can provide useful insights into the relationship between population level factors or behavioural variables and HIV prevalence in the general population. These findings may then be used to inform model development. Deterministic dynamic modelling used in this thesis demonstrates that the size and sexual networks of vulnerable subgroups in the population may be of key importance in determining levels of HIV epidemics in West Africa. In-particular, adolescent females engaging in noncommercial multiple partnerships, often associated with transactional exchange are an important determinant of the HIV epidemic in West Africa. An improved understanding of this group, their size and motivations for engaging in multiple partnerships, through the use of epidemic mapping techniques and social research, will be important to future HIV intervention activities.

Despite medical advances, HIV and AIDS remain incurable. The promotion of safer sexual practices has therefore seemed crucial. However providing information has had limited success in changing behaviour. There are still many new cases of infection each year. In order to help plan effective interventions, researchers have explored peoples attitudes and beliefs around sex, and their associations with behaviour. I suggest that research, through reliance on social cognition models which are individualistic in focus. has neglected wider issues such as socio-cultural contexts of attitudes and behav iour. Such issues are likely to be important. I argue in Chapter One that information about sex and risk has not been delivered ·neutrally·. but rather in the context of messages which contain strong political and social agendas pertaining to sexual it) and moral it). Qualitative work has suggested that issues of pm,er. trust and romance are important in men's constructions and experience of safer sex. Differences have emerged between heterosexual and gay men in these respects. However, because studies have tended to include either gay or heterosexual men. comparisons between heterosexual and gay samples have been difficult. The present qualitative study aimed to explore how men understand HIV risk and safety. It also aimed to explore men's experiences of safer or riskier sexual behav iour. considering relationship and contextual factors as well as individual ones. Semistructured interviews were carried out with heterosexual and gay men in order to allow consideration of any emerging differences between accounts. Interviews were analy sed according to the principles of lnterpretative Phenomenological Analysis. Emerging material was constructed as themes which were eventually organised according to the following Master Themes: Definitions of Risk, Perceived Threat of HIV, Control and Negotiation, What Testing Does and Barriers. These themes are discussed in terms of their implications for intervention. Finally, I discuss quality of the research in terms of issues such as reliability, generalisability and reflectivity.

The present study employed qualitative methodology in order to explore the experiences of HIV disclosure among immigrant women living with HIV in the UK. It aimed to explore individual, relational and contextual factors influencing disclosure process. In-depth semi-structured interviews were conducted with six immigrant women living with HIV in the UK and Interpretative Phenomenological Analysis (IPA) was used to analyse the data. The study identified four main themes reflecting women's experiences of HIV disclosure: (1) stigma, discrimination and disclosure; (2) dealing with the negative outcomes of disclosure; (3) disclosure as a relational process and (4) positive outcomes of disclosure. Overall, the findings highlight the complexity of the disclosure process and the multiple factors impacting on HIV disclosure. One of the most striking findings is the impact of stigma and discrimination on HIV disclosure and the extent to which women in the present study experience 'double stigma' - as people living with HIV within African communities and as immigrants within the UK. Another aspect reflected in women's accounts is the relationship between disclosure and adjustment to HIV diagnosis. Thus, disclosure is viewed as both depending on and contributing to adjustment to HIV diagnosis. Furthermore, women's disclosure decision making process is embedded in the interpersonal relationships and highlights multiple relational factors influencing women's decisions, including reactions of others, fear of rejection, the nature of relationship and timing of disclosure. Finally, women's disclosure is characterised by their sense of responsibility towards protecting others. The study outcomes are discussed in relation to the existing literature and the findings unique to this study are highlighted. The implications of the findings are discussed in relation to clinical practice and support for immigrant women living with HIV in the UK. Furthermore, suggestions for the future research are outlined.