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How did imported diseases affect Indigenous peoples after European arrival in the Americas?

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Map showing the transatlantic and global routes of major early voyages of discovery and exploration by Spain, Portugal, England, and France during the 15th and 16th centuries. The map traces the journeys of explorers such as Columbus, Cabot, Magellan, da Gama, and others, with labeled paths crossing the Atlantic and encircling Africa and South America, as well as lines of demarcation dividing Spanish and Portuguese exploration zones. — European exploration Map depicting the European exploration of the New World in the 15th and 16th centuries, including the voyages made by Christopher Columbus, John Cabot, Alonso de Ojeda and Amerigo Vespucci, Pedro Álvares Cabral, Ferdinand Magellan and Juan Sebastián del Cano, Giovanni da Verrazzano, Jacques Cartier, Sir Francis Drake, and others. The lines of demarcation represent an early division between the territory of Spain (to the west) and Portugal (to the east).

The arrival of Europeans in the Americas introduced a suite of acute infectious diseases to which Indigenous peoples had no prior exposure or immunity, including smallpox, measles, influenza, mumps, typhus, and whooping cough. Because these populations had not previously hosted these pathogens—which were endemic in Eurasia and Africa—the resulting epidemics were catastrophic.1

The demographic impact was profound, with population declines across the Americas estimated between 50 percent and 95 percent by 1650. In the Caribbean, the loss was even more severe, with populations plummeting by more than 99 percent by 1600.1

These biological effects were compounded by secondary factors, including famine, pneumonia, forced labour, and mass violence. While some scholars emphasize the devastating mortality caused by these diseases, others note that this focus should not obscure the resilience of Indigenous peoples who survived and adapted in the face of colonialism.123