First, I would like to thank my supervisor Prof. Tom Smith for his support during the years that this thesis was in progress, for his professional guidance, scientific insights and generous help, particularly on my last working trip to the STI. I consider myself very fortunate to have benefited from his expertise. Many thanks to him and his wife Julie for hosting me so kindly in Basel on more than one occasion. Likewise I sincerely appreciate the kind efforts of Dr Immo Kleinschmidt and Dr

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... ope Vounatsou, who patiently taught me so much of what I know about statistics. Most of the statistical work in this thesis would have been quite impossible without their guidance. Sincere thanks to Dr Musa Mabaso, helpful critic of numerous manuscripts and co-worker in the MARA project. It is always a pleasure working with him. Thanks Musa, we have come a long way together. I sincerely wish to acknowledge Dr Brian Sharp, recently deceased. I am extremely grateful for the privilege of having experienced his leadership. He was and remains a role model to me, a mentor, a guide. With sound motives and the bigger picture in mind, he was neither petty nor negative, but always saw the potential in people and situations. He did all in his power to support working mothers. I valued his opinion enormously and miss him very much. I would also like to acknowledge Dr David le Sueur, also deceased, who gave me valuable guidance during the early days of my career. He set me on a course of modelling malaria distribution, by sending me for training in Idrisi in the USA, guiding the development of the malaria distribution model, and then employing me as GIS coordinator in the MARA project. Sincere thanks go to the other MARA collaborators, in particular Prof. Christian Lengeler and Prof. Don de Savigny, for their availability, support and commitment from the start of the Acknowledgements vii project until today. They were a major source of practical help, good advice and inspiration, and remain valued friends and allies. Prof. Lengeler was also the principal instigator who urged me to consider registering for a PhD through the STI. Andrew's chocolate factory didn't quite pan out, but the rest did. Thank you also for hosting me in Basel so kindly. My gratitude also goes to Prof. Marcel Tanner for his enthusiastic support, and for giving me the opportunity of enrolling for doctoral studies through the STI, and to the STI and the Rudolf Geigy Stiftung zu Gunsten des Schweizerischen Tropeninstituts for supporting this study financially. I also value the support of the South African Medical Research Council, which grants its employees extended leave of absence so that we may pursue further study overseas. I greatly appreciate the many other colleagues and fellow-students, both at the Medical Research Council and the Swiss Tropical Institute, in particular Laura and Dominic Gosoniu, Amanda Ross, Nicholas Maire, Claudia Sauerborn, Sohini Banerjee, for, above all, your friendship, for many stimulating discussions (not always about work) and for all the good times. I never could have done this work in isolation. Thank you Andrew for your loving support and encouragement, especially when I felt like giving up. Thank you for accompanying me to Switzerland for 10 months, and for running the show back home during various shorter trips to Basel. Thank you Miriam and Philip for looking after dad when I was away. You are fantastic kids. Sincere thanks to my aunt Marianne Kassier who kindly translated the summary into German, and to Michael Bretscher for editing the "Fachdeutsch". I really appreciate your help. Finally, many thanks to Dr Jon Cox for agreeing to be the external examiner.