Why is cholera called the blue death?

Cholera is referred to as the "blue death" due to the severe dehydration it causes, which can lead to a dramatic drop in blood pressure and a bluish discoloration of the skin. This cyanosis can occur as the body struggles to maintain oxygen levels, giving affected individuals a bluish hue. The term highlights the severity and rapid progression of the disease, which can be fatal within hours if untreated.