PubMed1976
Various workers, including T. D. Stewart, claim that the aboriginal Americas were relatively disease-free because of the bering Strait cold-screen, eliminating many pathogens, and the paucity of zoonotic infections because of few domestic animals. Evidence of varying validity suggests that precontact Americns had their own strains of treponemic infections, bacillary and amoebic dysenteries, influenza and viral penumonia and other respiratory diseases, salmonellosis and perhaps other food poisoning, various arthritides, some endoparasites such as the ascarids, and several geographically circumscribed diseases such as the rickettsial verruca (Carrion's disease) and New World leishmaniasis and trypanosomiasis. Questionably aboriginal are tuberculosis and typhus. Accordingly, virtually all the "crowd-type" ecopathogenic diseases such as smallpox, yellow fever, typhoid, malaria, measles, pertussis, polio, etc., appear to have been absent from the New World, and were only brought in by White conquerors and their Black slaves. My hypothesis is that native American medical care systems--especially in the more culturally advanced areas--were sufficiently sophisticated to deal with native disease entities with reasonable competence. But native medical systems could not cope with the "crowd-type" disease imports that struck Indian and Eskimos as "virgin-field" populations. Reanalysis of native population losses through a genocidal combination of diease, war, slavery and attendant cultural disruption by Dobyns, Cook and others strongly suggest that traditiona estimates underplayed the death toll by a factor of the general order of ten. This would make for an immediately pre-contact Indian population of some 90-111 million instead of the tradition 8-11 million. Evidence is growing that Indians may have been no more susceptible to new pathogens that are other "virgin soil" populations, and thus their immune systems need not be considered less effective than those in other people. Present-day high mortality rates in Indians of both continents from infectious disease imports may be more socioeconomic than anything else.