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Native Americans in the United States |
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Although a variety of infectious diseases existed in the Americas in pre-Columbian times,[1] the limited size of the populations, smaller number of domesticated animals with zoonotic diseases, and limited interactions between those populations (as compared to areas of Eurasia and Africa) hampered the transmission of communicable diseases. One notable infectious disease that may be of American origin is syphilis.[1] Aside from that, most of the major infectious diseases known today originated in the Old World (Europe, Asia, and Africa). The American era of limited infectious disease ended with the arrival of Europeans in the Americas and the Columbian exchange of microorganisms, including those that cause human diseases. Eurasian infections and epidemics had major effects on Native American life in the colonial period and nineteenth century, especially.
Eurasia was a crossroads among many distant, different peoples separated by hundreds, if not thousands, of miles. But repeated warfare by invading populations spread infectious disease throughout the continent, as did trade, including the Silk Road. For more than 1,000 years travelers brought goods and infectious diseases from the East, where some of the latter had jumped from animals to humans. As a result of chronic exposure, many infections became endemic within their societies over time, so that surviving Europeans gradually developed some acquired immunity, although they were still vulnerable to pandemics and epidemics. Europeans carried such endemic diseases when they migrated and explored the New World.
Europeans often spread infectious diseases to Native Americans through trading and colonization efforts, and these could even be transmitted far from the sources and colonial settlements, including through exclusively Native American trading transactions. Warfare and enslavement also contributed to disease transmission. Because their populations were historically hygienic and had not been previously exposed to most of these infectious diseases, the indigenous people rarely had individual or population acquired immunity and consequently suffered very high mortality. The numerous deaths disrupted Native American societies. This phenomenon is known as the virgin soil effect.[2]