Diarrhea and its complications are the most important causes of infant death in most developing regions. The causes of the illness vary from dietary incompatibilities to intestinal infection. The most important infectious causes are, in approximate order of importance, rotavirus, the bacteria Campylobacter jejuni, Shigella (often causing dysentery or passage of bloody stools), Salmonella, and Escherichia coli, and the parasites Giardia lamblia, Cryptosporidium, and Entamoeba histolytica. The microorganisms are spread to the infant from other persons or through food or water. Breast-feeding is associated with a decreased occurrence of diarrhea and represents a major means of preventing infantile diarrhea in the developing world.