USA HISTORY

Detailed explanation-1: -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.

Detailed explanation-2: -Smallpox is believed to have arrived in the Americas in 1520 on a Spanish ship sailing from Cuba, carried by an infected African slave. As soon as the party landed in Mexico, the infection began its deadly voyage through the continent.

Detailed explanation-3: -Historian and demographer Nobel David Cook estimates that, in the end, the regions least affected lost 80 percent of their populations; those most affected lost their full populations; and a typical society lost 90 percent of its population.

Detailed explanation-4: -Old World diseases that were not present in the Americas until contact include bubonic plague, measles, smallpox, mumps, chickenpox, influenza, cholera, diphtheria, typhus, malaria, leprosy, and yellow fever.

Detailed explanation-5: -Unknown in the New World, smallpox was introduced by the Spanish and Portuguese conquistadors. The disease decimated the local population and was instrumental in the fall of the empires of the Aztecs and the Incas.