Why is cholera still a problem for many countries, even though people learned much about the disease and how it spreads during the London epidemic of 1846?

Today, cholera affects countries suffering from low development. Outbreaks occur in areas with poor sanitation, a lack of clean water, and limited access to proper healthcare. These countries often lack the necessary resources to prevent and treat outbreaks.

answer; native americans who sometimes actively impeded railroad construction; physical obstacles like rivers and canyons, and