Untreated cholera can cause a person to lose 10-15 liters of fluid per day. Patients experiencing severe fluid loss can go into shock and die within hours. Cholera can also cause the following health problems:

Hypotension (low blood pressure)
Hypokalemia (low potassium in the blood)
Increased heart rate
Dry mouth
Decreased skin turgor

Furthermore, the severe dehydration caused by untreated cholera can lead to:

Kidney failure
Shock
Coma
Death