Organisms that cause diarrhea invade the wall of the intestine or produce toxins. The infection causes swelling and irritation of the lining to the intestine. These infections spread through contaminated food or water.

Infectious causes for diarrhea include:

• Bacterial gastroenteritis:
• Cholera
• Salmonella infection
• Shigella gastroenteritis
• E. coli gastroenteritis
• Campylobacter enteritis
• Pseudomembranous colitis
• Food poisoning
• Traveler's diarrhea
• Viral gastroenteritis:
• Rotavirus infection
• Norwalk virus infection
• Viral hepatitis
• Herpes simplex virus
• Parasites:
• Giardiasis
• Entamoeba infection
• Cryptosporidium enterocolitis
• Pinworms
• Trichinosis
• Ciguatera poisoning
• Toxic shock syndrome