The only two nineteenth-century cholera visitations of record in Western Africa occurred in the Senegal and Gambia River valleys during the Fourth and Fifth Pandemics, in the years 1868–1869 and 1893–1894 respectively. On both occasions, the likely path of the infestation was by sea from the Mediterranean, though a caravan route from the Maghreb across the Sahara might have been possible.
The region bounded by the Senegal River valley in the north and the Gambia River valley in the south, and extending farther to what is now Guinea-Bissau, had long familiarity with international trade, both in slaves and in products such as gum arabic and ivory. Portuguese traders first arrived in the fifteenth century, and by the eighteenth century, mainly British and French merchants vied for control of the coastal factories and slave pens that were so significant in the involuntary migration of Africans across the South Atlantic. Beginning in the eighteenth century, devout new Muslim leaders led a series of religious wars against the established African polities. Despite failed attempts at tropical agriculture in the early nineteenth century, the European presence grew, often through the efforts of an Afro-European minority who became prosperous in the French and British coastal emporiums. These ambitious men helped European powers develop new trading posts up-river in the region, and they designed ambitious plans for the control and conquest of the interior.