USA HISTORY

Detailed explanation-1: -They had never experienced smallpox, measles or flu before, and the viruses tore through the continent, killing an estimated 90% of Native Americans.

Detailed explanation-2: -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-3: -Though warfare and attacks on entire villages took a definite toll on the populations of Native Americans, disease was by far the biggest killer.

Detailed explanation-4: -Between 1492 and 1600, 90% of the indigenous populations in the Americas had died. That means about 55 million people perished because of violence and never-before-seen pathogens like smallpox, measles, and influenza.