Cholera appeared in the United States for the first time in 1832. Subsequent outbreaks triggered epidemics in 1848-49, 1866, and 1873. Driven both by world-wide disease patterns and by regional demographics, cholera initially took hold in densely populated port cities like New York City and New Orleans, then followed trade routes to the interior of the continent. Cholera killed roughly half the people it infected. As scientific knowledge of cholera's bacterial causes emerged during the late nineteenth century, officials in some places, including New York City, succeeded in reducing the impact of the disease through sanitary reforms.