How does Cholera work?

Cholera works by releasing a toxin in the lumen. It causes chloride channels of the intestinal epithelial cells to open which in turn causes cholride ions to move along its concentration gradient into the lumen of the small intestine. This causes water to move via osmosis into the lumen of the small intestine (as the water potential of the lumen becomes more negative than the water potential of the epithelial cells) causing lots of water to be lost from the body. This causes severe dehydration which is how Cholera works.