I consider in this chapter the mobilities of five diseases, in a variety of historical contexts. First, I examine the impact of smallpox on the demographics of native middle and south American Indian populations in the 16th century. Next, I look at the spread of bubonic plague, before turning to cholera, influenza and measles. Clearly, I cannot do more than scratch the surface of disease spread, and the reader must turn to more specialist books and papers for in-depth treatments. My aim is to uncover some of the mechanisms of diffusion, in particular the mobilities of the actors involved, and the ways in which historical transport networks structured such spread. Some of these diseases are still very much with us, but in this chapter my focus will be on the historical context, and I defer to the following chapter a consideration of the impact of more recent strains of influenza.