What was one of the most deadly illnesses the pioneers faced how was it spread?

One of the most deadly illnesses faced by pioneers was cholera, which spread rapidly through contaminated water sources. Poor sanitation and limited access to clean drinking water made outbreaks common, particularly in crowded encampments or settlements. The disease could lead to severe dehydration and death within hours if not treated promptly. Other illnesses, such as smallpox and typhoid fever, also posed significant threats during westward expansion.