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Abstract: Infection ranks alongside cardiovascular disease as the major cause of human death across the world. Word Health Organization data for 2002 shows that 26% of all deaths, almost 15 million in number, were due to infectious disease with HIV/AIDS, TB and malaria being the top three responsible infections. A significant proportion of these deaths were due to lower respiratory infections and diarrheal diseases in children. The worldwide morbidity associated with infectious disease is incalculable. When considered along with the consequences of infection in animals, it is hard to imagine any other disease that has such a significant impact on our lives―on health systems, on agriculture and on world economics. Our understanding of the agents responsible for infections―bacteria, fungi, parasites, prions and viruses―has an interesting history that heralds the great developments in modern biology and demonstrates how an understanding of disease pathogenesis can lead to successful prophylactic and therapeutic interventions. Van Leeuwenhoek’s first observation of bacteria under the light microscope, John Snow’s investigations tracing the source of a cholera epidemic in Victorian London’s Soho and Pasteur’s vaccines for rabies and anthrax contributed to an acceptance of the germ theory of disease and to the rational, scientific application of this knowledge to develop innovative disease control measures ranging from hygienic practices to antibiotics. [...]