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
Other ways to get to Oregon were: using the York Factory Express route across Canada, and down the Columbia River; ships from Hawaii, San Francisco, or other ports that stopped in Oregon; emigrants trailing up from California, etc. All provided a trickle of emigrants, but they were soon overwhelmed in numbers by the emigrants coming over the Oregon Trail.