Changing Risk Behaviours and the HIV Epidemic: A Mathematical Analysis in the Context of Treatment as Prevention

Abstract

BackgroundExpanding access to highly active antiretroviral therapy (HAART) has become an important approach to HIV prevention in recent years. Previous studies suggest that concomitant changes in risk behaviours may either help or hinder programs that use a Treatment as Prevention strategy.AnalysisWe consider HIV-related risk behaviour as a social contagion in a deterministic compartmental model, which treats risk behaviour and HIV infection as linked processes, where acquiring risk behaviour is a prerequisite for contracting HIV. The equilibrium behaviour of the model is analysed to determine epidemic outcomes under conditions of expanding HAART coverage along with risk behaviours that change with HAART coverage. We determined the potential impact of changes in risk behaviour on the outcomes of Treatment as Prevention strategies. Model results show that HIV incidence and prevalence decline only above threshold levels of HAART coverage, which depends strongly on risk behaviour parameter values. Expanding HAART coverage with simultaneous reduction in risk behaviour act synergistically to accelerate the drop in HIV incidence and prevalence. Above the thresholds, additional HAART coverage is always sufficient to reverse the impact of HAART optimism on incidence and prevalence. Applying the model to an HIV epidemic in Vancouver, Canada, showed no evidence of HAART optimism in that setting.ConclusionsOur results suggest that Treatment as Prevention has significant potential for controlling the HIV epidemic once HAART coverage reaches a threshold. Furthermore, expanding HAART coverage combined with interventions targeting risk behaviours amplify the preventive impact, potentially driving the HIV epidemic to elimination.

Does size really matter? A sensitivity analysis of number of seeds in a respondent-driven sampling study of gay, bisexual and other men who have sex with men in Vancouver, Canada

“…The scale-up of highly active antiretroviral therapy (HAART) in BC through a policy of Treatment as Prevention may affect HIV sexual risk behaviour as mediated by increasing use of soft and hard drugs (including injection and non-injection drugs) [26]. If this risk compensation is substantial, then the HAART scale-up might not bring about a decline in HIV incidence in the GBMSM population.…”

Sexual behavior, risk perception and HIV transmission can respond to HIV antiviral drugs and vaccines through multiple pathways

“…Over the past few decades, our growing understanding of factors contributing to HIV transmission has improved HIV control efforts. Partner selection and safe sex practices are now recognized as major determinants of HIV prevalence 1 2 and have been analyzed through mathematical models focussing on behavioral aspects of HIV and other sexually infectious diseases 3 4 5 6 . This remains an important issue, particularly with data indicating that, despite greater public awareness, HIV incidence rates are once again increasing in men who have sex with men (MSM) in the United States 7 .…”

“…Epidemiological models such as disease transmission models or game theoretical models can be used to address how disease dynamics unfold over time and influence risk perception and behavior in a single population 3 4 5 6 18 19 20 . Previous disease transmission models have addressed the issue of how HAART optimism may occur and how it may influence disease dynamics and/or behavior.…”

“…Previous disease transmission models have addressed the issue of how HAART optimism may occur and how it may influence disease dynamics and/or behavior. For example, Ramadanovic et al focus on changing risk behaviors in the context of preventive HIV treatment 3 . The authors create a deterministic compartmental model that treats HIV risk behavior and infection as linked processes wherein the individual increases risk behavior as a precursor to contracting HIV.…”

Antiretroviral therapy for prevention of HIV transmission: implications for Europe

“…Modelling studies have explored the widespread use of ART but mainly in sub-Saharan settings [72][73][74][75][76][77][78][79][80][81][82][83][84][85][86][87][88][89], in the United States [90;91], in China [92][93][94], Canada [95] and for some specific groups, such as MSM in Australia [36;96;97], in Peru, Ukraine, Kenya and Thailand [98] and in different cities in the United States [99][100][101][102][103]; only a few of them model the HIV epidemic in European countries (MSM in Amsterdam, the Netherlands [104] and in the UK [105][106][107] and people who inject drugs in Russia [108]). They varied in their conclusions, although most have suggested potential appreciable beneficial effects on HIV incidence of introducing ART initiation at a higher CD4 count as a policy at a population level.…”