The patient is a female, age 19. She was admitted to the hospital for prolonged diarrhea. The patient is an anthropology major attending school in Madison, WI. She is in a monogamous relationship and is sexually active. She is allergic to wasp and bee venom. She has a family history of Alzheimer's disease. She lives with one roommate in student housing. She does not own any pets herself; however, she often cares for her roommate's turtle (a red-eared slider). Over her most recent spring break she took several short trips. First, she and her boyfriend went camping in the woods for a night. A few days later, she and her roommate spent 6 days in Cancun, Mexico, with several other friends. During the last few days of her trip, she began to feel unusually tired and occasionally nauseous, with abdominal cramping and increased flatulence. Following her return to the US, the frequency of her bowel movements increased from roughly once every day, to an average of four times a day. In addition, her bowel movements have become loose, off-colored (pale), and occasionally watery. She has lost roughly 5 lbs since returning from her trip. Neither her roommate nor boyfriend has shown any signs of illness.