Introduction

Throughout history in the Indian Ocean World (IOW) diseases have, under certain distinctive geographical and climatic conditions, emerged and spread, generating a number of impacts on varying spatial scales. This macro-region running from Eastern Africa to East Asia is affected by various environmental factors—the most significant of which is the monsoon system. Far from having been stable the monsoon system could unpredictably fail, triggering drought, crop failure, famine, and disease. Heavy monsoons, cyclones, seismic activities, tsunamis, and storm surges could lead to flooding that might in turn create favourable conditions for pathogenic microorganisms and thus for the spread of water-borne and contagious diseases. Weather extremes and natural disasters were often followed by famines, conflict, and migration, all of which increase health hazards. The IOW witnessed the rise of the first “global” economy from around 300 BCE. The IOW global economy, linking Eastern Africa and the Middle East to China through the creation of a sophisticated network of overland, riverine, and maritime communication, was characterized by an intensifying exchange of plants, animals, and (both voluntary and involuntary) humans—creating the quintessential conditions for disease diffusion in the macro-region.