USA HISTORY

Detailed explanation-1: -When Europeans began to explore and colonize other parts of the world, smallpox traveled with them. The native people of the Americas, including the Aztecs, were especially vulnerable to smallpox because they’d never been exposed to the virus and thus possessed no natural immunity.

Detailed explanation-2: -Before 1492, Native Americans (Amerindians) hosted none of the acute infectious diseases that had long bedeviled most of Eurasia and Africa: measles, smallpox, influenza, mumps, typhus, and whooping cough, among others.

Detailed explanation-3: -Diseases such as treponemiasis and tuberculosis were already present in the New World, along with diseases such as tularemia, giardia, rabies, amebic dysentery, hepatitis, herpes, pertussis, and poliomyelitis, although the prevalence of almost all of these was probably low in any given group.

Detailed explanation-4: -European explorers unwittingly brought with them chickenpox, measles, mumps, and smallpox, decimating some populations and wholly destroying others. One disease did travel the other direction-syphilis, a lethal sexually transmitted disease, came with travelers from the New World to Europe for the first time.