The purpose of this study was to observe the natural progression of untreated syphilis in rural African-American men in Alabama under the guise of receiving free health care from the United States government.
1 Diarrhea is caused by increased secretion of fluid into the intestine, reduced absorption of fluid from the intestine or rapid passage of stool through the intestine.  Symptoms associated with diarrhea include abdominal pain, especially cramping. Other symptoms depend on the cause of the diarrhea.
Numerous bacteria, viruses, and parasites cause diseases in the intestines that result in diarrhea, dysentery, constipation or perianal irritation. They may also cause nausea, vomiting, and abdominal cramping. If the infection is in the small intestine, symptoms include watery diarrhea and vomiting. Infections in the large intestine can cause diarrhea and can result in an invasive and inflammatory disease called dysentery (small fecal volume with mucus and blood) (Table SI-1). Table SI-1.