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Measles and TB evolved from diseases of our cattle, influenza from a disease of pigs, and smallpox possibly from a disease of camels. The Americas had very few native domesticated animal species from which humans could acquire such diseases.
麻疹和结核病是由牛的疾病演变而来，流感是由猪的疾病演变而来，天花可能是由骆驼的疾病演变而来。美洲本土的驯养动物种类很少，人类可以从这些动物身上获得这种疾病。