Smallpox Devastates the Americas

When Spanish conquistadors arrived in the Americas in the early 16th century, they carried a weapon far deadlier than their guns: smallpox. The disease, to which Indigenous peoples had no immunity, arrived in Hispaniola by 1507 and reached the Aztec capital Tenochtitlan by 1520, killing an estimated 5–8 million people in central Mexico alone. The Inca Empire was similarly devastated before Pizarro even arrived. Across the Americas over the following centuries, smallpox and other European diseases — measles, typhus, influenza — killed an estimated 90% of the pre-Columbian population, perhaps 55 million people. This demographic catastrophe, often called the "Great Dying," was the largest loss of human life in history and fundamentally shaped the colonial world that followed.