Cholera outbreaks and pandemics
That year, cholera was transmitted along the California, Mormon and Oregon Trails as 6,000 to 12,000 are believed to have died on their way to the California Gold Rush, Utah and Oregon in the cholera years of 1849–1855. It is believed more than 150,000 Americans died during the two pandemics between 1832 and 1849.
Oregon Trail
Overall, some 268,000 pioneers used the Oregon Trail and its three primary offshoots, the Bozeman, California, and Mormon trails to reach the West Coast, 1840-60. Another 48,000 headed to Utah. There is no estimate on how many used it to return East.