In Latin America, Chagas disease, caused by infection with Trypanosoma cruzi, is a prime example of this co-evolutionary process in which parasites and mammalian reservoirs (including humans) are engaged in a dynamic race of ecological adaptation and counter-adaptation. In the search for improved sources of income, agriculture, livestock rearing, and other socioeconomic activities, human populations began migrating into the natural wild habitats where T. cruzi infection was enzootic. Ultimately, poverty, poor housing and sub-standard living conditions, deforestation, and other ecological factors promoted an adaptation of triatomine vectors to both humans and domestic animals, with increased efficiencies of the wild, domestic, and peridomestic cycles of T. cruzi transmission. Once humans became infected and acted as a reservoir for the infection, other forms of transmission also evolved through blood transfusion, congenital transmission, and organ transplantation. In some settings, oral transmission through contaminated food is now considered an important mode of transmission.