Infectious diarrhea<unk>  in the<unk>  is caused by various bacteria, viruses, and parasites (protozoa). The most commonly reported are the protozoa Giardia and Cryptosporidium. Other infectious agents may play a larger role than generally believed and include Campylobacter, hepatitis A virus, hepatitis E virus, enterotoxogenic E. coli, E. coli O157:H7, Shigella, and various other viruses. More rarely, Yersinia enterocolitica, Aeromonas hydrophila, and Cyanobacterium may also cause disease. Giardia lamblia cysts usually do not tolerate freezing although some cysts can survive a single freeze–thaw cycle. Cysts can remain viable for nearly three months in river water when the temperature is 10 °C and about one month at 15–20 °C in lake water. Cryptosporidium may survive in cold waters (4 °C) for up to 18 months, and can even withstand freezing, although its viability is thereby greatly reduced. Many other varieties of diarrhea-causing organisms, including Shigella and Salmonella typhi, and hepatitis A virus, can survive freezing for weeks to months. Virologists believe all surface water in the United States and Canada has the potential to contain human viruses, which cause a wide range of illnesses including diarrhea, polio and meningitis. Modes of acquiring infection from these causes are limited to fecal-oral transmission, and contaminated water and food. The major factor governing pathogen content of surface water is human and animal activity in the watershed.
Wilderness-acquired diarrhea
Antibiotic-associated diarrhea
Travelers' diarrhea
Factitious diarrhea
Porcine epidemic diarrhoea
Riga–Fede disease
Food protein-induced enterocolitis syndrome
Brainerd diarrhea