This dissertation uses a wide variety of original historical sources to examine Nahua (Aztec) and Spanish concepts of health and sickness in the sixteenth century, and how both cultures applied these concepts in their attempt to understand the widespread, devastating epidemics that plagued colonial Mexico or New Spain. The Nahuatl and Spanish texts of the Florentine Codex and the Relaciones Geogr�ficas, in addition to several other pictorial and alphabetic writings, abound with information on a topic that is little explored and poorly understood: how did indigenous peoples comprehend and remember the terrible, recurring diseases that wiped out about 90% of their population over the course of a century? How did they associate disease with the arrival of the Spaniards, the conquest, Christianity, and colonial rule? How did they speak and write about these matters? And how did their words on these topics differ from what the Spaniards said? How did Spanish cultural concepts, based on Greek, Roman, and Christian understandings of the body, conform with and contradict Nahua beliefs and practices. What were the implications of the similarities and differences? How did the dominant group attempt to discredit native practices and beliefs regarding health and illness that they considered pagan or superstitious? Did Nahua concepts persevere and survive?

This dissertation addresses these questions for the Nahuas of central Mexico, focusing on the period from 1519 to 1615, a period in which at least three major epidemics ravaged the indigenous population of New Spain. But the findings are applicable to all parts of the Americas in the early modern or colonial period, up until the early nineteenth century, when nearly all indigenous peoples in the hemisphere came into contact with Europeans and Africans and the pathogens that they carried with them across the Atlantic Ocean. Many works have addressed the nature of the epidemics and the extent of the demographic decline, but few studies in the Latin American field of history and related disciplines have endeavored to recover indigenous voices on this topic.

This dissertation contributes to the research of ethnohistorians who seek to recover indigenous perspectives of history by reading numerous different types of historical sources, including native-language alphabetic documents and pictorial writing systems. By correlating historical evidence from the colonial period with ethnographic evidence from the modern period, I show how certain Nahua and Mesoamerican beliefs and practices about health, sickness and healing have endured in Mexico today, despite all odds. This dissertation also contributes to the history of science in the Spanish colonial world by examining texts on medicine produced by indigenous authors and healers, knowledge that was sought after by Europeans. Finally, this interdisciplinary study enhances our understanding of a deadly trans-Atlantic exchange from the perspective of indigenous peoples who managed to survive and record their experiences.