The American Indians had no immunity to these illnesses. The first century after contact was the most disastrous, between 1520 and 1600 31 major epidemics swept across the land. The Indians died quickly after exposure to these epidemics. The Indian population of North America fell from about five million at contact to three million individuals within 100 years (Mihesuah, 1996). One reason that such epidemics were so destructive was that without any immunity whatsoever the American Indian population was nearly all afflicted or infected by a disease at the same time. Another reason was the inferior medical practices employed by the Indians, such as sweat houses, herbs, and spiritual prayer were grossly inadequate for these Eastern spawned illnesses (Thornton, 1942).
Of the diseases introduced from these Eastern Hemisphere, the greatest early killers of American Indians were smallpox, typhus, and measles with smallpox probably being the most devastating of the three (Thornton, 1942). Europeans quickly learned of Indians susceptibility to diseases, and in 1763 British officers led by Lord Jeffrey Amherst sent blankets infected with smallpox to Ottawa's and other tribes in deployment of ea