Chapter 1 starts by describing how, shortly after HIV was identified as the cause of AIDS, it became increasingly clear that the virus originated in Africa. Tests of archival blood samples, retrospective confirmation of early cases of AIDS and comparison of the genetic diversity of HIV in different parts of the world all pointed to central Africa, and especially the two Congos, as the probable location for the beginning of HIV’s journey. Studies of HIV subtypes provide the foundation for reconstructing the complex routes followed by the virus across the world. The example of Cuba illustrates how geopolitical events influenced the spread of HIV. The first epidemic of Ebola fever in a bush hospital in the Congo, as well as recent epidemics in the same country and in West Africa, are used to explain the peculiar characteristics of HIV that enabled it to cause a pandemic.