Why did European diseases cause such a massive decline in Indigenous populations during the Columbian Exchange?

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Columbian Exchange Christopher Columbus arriving in the New World, illustration in *Il costume antico et moderno* (“The Ancient and Modern Costume,” (1817–26).

During the Columbian Exchange, European diseases caused a massive decline in Indigenous populations primarily because these populations had no prior exposure or immunity to illnesses such as smallpox, measles, and influenza. These diseases, which were endemic and often survived by Europeans, became devastating epidemics in the Americas. The lack of immunity meant that mortality rates could reach as high as 95 percent, compounded by the stress of violence and displacement. This one-sided exchange of diseases significantly impacted the demographic landscape of the Americas.123