Francisco Hernández de Toledo was a naturalist and court physician to Philip II of Spain. He was among the first wave of Spanish Renaissance physicians practicing according to the revived principles formulated by Hippocrates, Galen and Avicenna.

The Cocoliztli Epidemic or the Great Pestilence was an outbreak of a mysterious illness characterized by high fevers and bleeding which caused 5–15 million deaths in New Spain during the 16th century. The Aztec people called it cocoliztli, Nahuatl for pestilence. It ravaged the Mexican highlands in epidemic proportions, resulting in the demographic collapse of some Indigenous populations.