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The role of sexual behaviour dynamics and treatment-as-prevention in the spread of HIV, Hepatitis C and syphilis: Predicting the conditions for control and elimination

English title The role of sexual behaviour dynamics and treatment-as-prevention in the spread of HIV, Hepatitis C and syphilis: Predicting the conditions for control and elimination
Applicant Rauch Andri
Number 179567
Funding scheme Project funding (special)
Research institution Inselspital, Universitätsspital Bern Universitätsklinik für Infektiologie
Institution of higher education University of Berne - BE
Main discipline Infectious Diseases
Start/End 01.07.2018 - 30.06.2023
Approved amount 686'074.00
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All Disciplines (2)

Infectious Diseases
Methods of Epidemiology and Preventive Medicine

Keywords (13)

HIV; HCV; syphilis; large nested project; Transmission model; Risk beahviour; HIV; Epidemic; HCV; Syphilis; Large nested project; Prevention; SHCS

Lay Summary (German)

Jedes Jahr versterben mehr als 1 Million Menschen weltweit an den Folgen von sexuell übertragenen Infektionen. Im Falle von HIV, Syphilis und Hepatitis C stagniert oder steigt die Anzahl von Neu-Infektionen trotz sehr effektiver Behandlungen. Das Projekt soll Erkenntnisse liefern, wie die weitere Verbreitung dieser Infektionen vermindert werden kann.
Lay summary

Inhalt und Ziel des Forschungsprojektes

Der Wandel des sexuellen Risikoverhaltens und neue Behandlungsmöglichkeiten beeinflussen die Rate von Neuinfektionen mit HIV, Hepatitis C oder Syphilis. In diesem Forschungsprojekt untersuchen wir folgende Fragen in Bezug auf die Epidemie dieser Infektionen:

- Wie hat sich das Risikoverhalten gewandelt und wie beeinflusst dies die Anzahl Neu-Ansteckungen?
- Korrelieren ähnliche Verhaltensweisen mit Übertragung-Netzwerken?
- Inwiefern kann eine medikamentöse Therapie die Ausbreitung von Infektionen verhindern?
- Welche präventiven Massnahmen sind notwendig, um die Verbreitung von HIV, Hepatitis C und Syphilis zu beenden?

Wissenschaftlicher und gesellschaftlicher Kontext

Das Projekt nutzt quantitative und qualitative Forschungsmethoden um die Wechselwirkung zwischen sexuellem Risikoverhalten, medikamentösen Therapien und der Übertragung von Infektionskrankheiten besser zu verstehen. Diese Information wird entscheidend sein bei der Planung und Durchführung von Massnahmen, welche diese Infektionskrankheiten eliminieren.

Direct link to Lay Summary Last update: 01.05.2018

Responsible applicant and co-applicants


Project partner

Associated projects

Number Title Start Funding scheme
177499 Swiss HIV Cohort Study (SHCS) 01.01.2018 Cohort Studies Large
146143 Understanding and Predicting the Hepatitis C Epidemic in HIV-infected Patients 01.05.2013 Project funding (special)


Control and elimination of HIV, hepatitis C Virus (HCV) and syphilis transmissions is a clinical and research priority worldwide. Available treatments options, including recent therapeutic breakthroughs4, dramatically improve the health of infected individuals and substantially lower the risk of onward transmission. Yet, even in countries with high diagnosis and treatment rates such as Switzerland, we and others have shown that the incidences of HIV, HCV and syphilis associated with sexual risk behaviour have not declined. In order to overcome barriers to transmission control and elimination, well-orchestrated prevention initiatives which expand the current fragmented approaches are needed. This can only be achieved by an improved understanding of the complex interplay between prevention and treatment strategies, patterns of sexual behaviour, and sexual contact networks. This project will comprehensively address these questions by combining established and novel methodologies, and by exploiting unique nationwide data sources. For decades, Swiss surveillance systems and the Swiss HIV Cohort Study (SHCS, have collected information on sexual behaviour in both HIV-negative and positive people, long-term incidence and clinical data, as well as viral genomic data. To the best of our knowledge, this will be the first study to jointly investigate sexual behaviour dynamics among HIV-negative and positive individuals, transmission networks inferred from viral phylogenies, and clinical outcomes for these three interacting infections. The overarching aim of this project is to identify the necessary conditions regarding sexual behaviour, diagnosis and treatment rates to control sex-related transmission of HIV, HCV and syphilis, and to characterize effective interventions to achieve transmission control. This project will determine whether and how WHO elimination targets (90% reduction in transmissions by 2030) are achievable. We intend to set-up coupled mathematical models of sexual behaviour, and HIV, HCV and syphilis transmission. The models will emulate the past and project the future of these epidemics. A routine update procedure will enable the models to continuously learn from newly upcoming data and to produce projections that reflect all known relevant information at time of projection. This project will provide a platform for the study of further STI such as gonorrhoea and chlamydia. The project will first focus on men who have sex with men (MSM) to subsequently extend the methodology to other transmission groups. The proposed methodology can be applied to other regions and to other transmissible diseases. In particular, we aim:Aim 1: To disentangle and model sexual behaviour structures and their relationship with transmission networks inferred from viral phylogenies. We will do this by: i) using unsupervised machine learning to infer clusters of sexual behaviour based on longitudinal individuals’ records; ii) characterizing the relationship between behavioural clusters and transmission networks inferred from phylogenetic analyses of HIV and HCV; iii) using behavioural clusters, transmission networks and their relationships to inform the sampling process of a qualitative nested study aimed at overcoming information gaps on sexual behaviour that have historically led to oversimplified assumptions; iv) developing a mathematical model that based on the outcomes of (i-iii) emulates the dynamics of sexual behaviour. The model of sexual behaviour will capture the effects of interactions between individuals and external information (e.g., scientific releases, media coverage of disease outbreaks) including public health interventions like campaigns aimed at influencing sexual behaviour.Aim 2: To model transmission of HIV, HCV and syphilis. We will integrate the model of sexual behaviour into previously developed models of HIV and HCV transmission, and will develop a model for syphilis transmission. These transmission models will be coupled to reflect interactions between the three infections, and time-updated to capture emerging information. Aim 3: To identify and project the impact of novel strategies for transmission control by exploiting the knowledge gained from Aims 1 and 2. Our models will identify target groups in which behavioural and treatment interventions are most likely to lead to the largest possible reduction in the incidence of the studied infections, and project the impact of such interventions. Modelled interventions will include treatment-as-prevention (TasP) and HIV pre-exposure prophylaxis (PrEP). Interventions will consider different scenarios of future sexual behaviour. Time-updating projections will provide a novel tool to this field for implementing and surveying interventions to contain STI transmission, and a mechanism for assessing and improving the accuracy of model projections.