An intestinal disease that causes diarrhea, giardiasis is one of the most common illnesses worldwide. It affects an estimated 20 percent of the world's population. It is most prevalent in developing countries, where infections are often associated with poor sanitary conditions.
Giardiasis is caused by a one-celled parasite called Giardia intestinalis. Besides diarrhea, this illness can cause abdominal pain, vomiting, and a host of other symptoms. The condition is more common in children; however, adults are more prone to chronic cases. Treatment often involves medications and staying well hydrated.
(To learn more about this disease, including what you can do to reduce your risk, click Giardiasis.)