Browsing by Author "Malunguza, N. J."

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    Malunguza, N. J. 2016. MATHEMATICAL MODELLING AND ANALYSIS OF EXISTING AND EMERGING PROBLEMS INFLUENCING THE TRANSMISSION DYNAMICS OF HIV/AIDS IN AFRICAN HETEROSEXUAL SETTINGS. PhD Thesis.
    (2016) Malunguza, N. J.
    The human immunodeficiency virus (HIV) is spread through exchange of body fluids and affects specific cells of the immune system, called CD4 + T cells. Progressive depletion of these cells over time leads to a condition called the acquired immuno deficiency syndrome (AIDS). In Africa, transmission in the general population is predominantly heterosexual. Confluence of various complex social, cultural and behavioural tendencies influence the incidence and distribution of the virus in the region and there are sub-populations that are particularly at heightened risk of acquiring or passing on the virus. In this thesis, HIV transmission models are formulated to obtain qualitative and quantitative insights into the transmission dynamics of the disease. The models are designed to capture the effect of differential infectivity and susceptibility through stratification of the population into sub-groups according to some risk factors peculiar to the group. Alcohol consumption in sexual settings reflective of gender inequities and same sex interaction between men and men in heterosexual settings are studied as inherently problematic pre-existing risks. Super-infection by different HIV subtypes, contraceptive use and heterosexual anal intercourse are also considered as emerging challenges in disease control. The models are rigorously analysed using analytical and computational techniques to determine solutions and their dynamical properties and transmission characteristics. Results show that superinfection by two non-competing HIV strains increases disease burden and must be factored in the HIV policing framework. Partnership formation rates between low and high risk groups are shown to be pivotal in the spread of HIV across heterogeneous populations so that constraining formation of partnerships between the general population and high risk groups such as alcohol consumers and men who have sex with men will be beneficial in the fight against HIV. Whereas literature on the acquisition and transmission risk posed by hormonal contraceptive use remains inconclusive, model results indicate the potential for accelerated spread and the bridging effect of men who may be the link between the high risk hormonal contraceptive users and the low risk general population. The model fit to data for Zimbabwe supports heterosexual anal intercourse (AI) only by a small percentage (< 1%) of the population in order for parameters to remain plausible with results showing that even at that low prevalence, heterosexual AI would compound HIV transmission. Study results show that MSM increase HIV spread in heterosexual settings through their bisexual activities and that curtailing bisexuality would overally have a negative impact on HIV spread. To bridge the gap between theory and real world observations, some models were fitted to sentinel data for Zimbabwe. Although data at the onset of the epidemic is sparse, an estimate of the basic reproductive number R0 quantifying the magnitude of the control effort necessary for epidemic control, was drawn. Projections of incidence and prevalence are made to allow for forward planning. Results from the assessment of each individual model collectively contribute to the general understanding of the problem surrounding the population level transmission dynamics of HIV for effective disease prevention and control.