MSc (Mathematcs) / Department of Mathematics and Applied Mathematics / Infectious diseases remain a major public health concern. Well-known for causing sickness and death, enormous pain and suffering, increased time spent on patient care and huge economic losses due to lost production. Infectious diseases continue to be a scourge without equal. In this work, we address the following research question: Can we use a multiscale model of HIV/AIDS transmission dynamics to assess the comparative effectiveness of health interventions that are implemented at different scale domains? To achieve the set objectives of the study, we use multiscale modelling approach, a new and emerging computational high-throughput technique for mathematically studying problems that have many characteristics across several scales. To be more specific, we perform three tasks in addressing the research question. First, we develop a within-host submodel and use it to show it’s associated limitations which only a multiscale model can resolve. Second, we develop a between-host submodel and use it to motivate the need for multiscale modelling of the HIV/AIDS disease system. Finally, we link the two submodels to produce a nested HIV/AIDS multiscale model that affords us the opportunity to compare effectiveness of five preventive and treatment HIV/AIDS health interventions. Analysis of the multiscale model shows that it is possible to jointly study two key aspects (immunology and epidemiology) of infectious diseases. The multiscale model provides the means for making meaningful comparative effectiveness on available preventive and treatment health interventions. Consequently, we employ the multiscale model to show that impact of HIV/AIDS packages increases as more interventions are integrated into the packages. Specifically, the study shows that combined HAART and male circumcision is more effective than an intervention involving HAART alone. Overall, our study successfully illustrates the utility of multiscale modelling methodology as a tool for assessing the comparative effectiveness of HIV/AIDS preventive and treatment interventions. For purposes of informing public health policy, we use the study results to infer that condom use, male circumcision and pre-exposure prophylaxis are more effective in controlling the transmission dynamics of HIV/AIDS at the start of the epidemic as compared to when the disease is endemic in the community while the converse is also true for HAART. / NRF