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Infectious diarrhea
Classification and external resources
ICD-9 009.2
eMedicine topic list
MeSH D004403
See also Gastroenteritis and Enteritis

Infectious diarrhea or Contagious diarrhea may be defined as diarrhea caused by an infection of the digestive system by a bacterium, virus, or parasite that results in frequent bowel motions producing excessive amounts of liquidy feces.[1]



This can usually be presumed to be infective, although only in a minority of cases is this formally proven.


The diarrhea is usually viral in origin, and is mostly caused by Norovirus, Rotavirus, Adenovirus, or Astrovirus.

Viruses, particularly rotavirus, are common in children. (Viral diarrhea is probably over-diagnosed by non-doctors). Norwalk virus (i.e. norovirus) can also cause these symptoms.

Bacteria and their toxins

Common organisms include Campylobacter jejuni and Salmonella, both typically acquired from animal food products. Often "food poisoning" is really Salmonella infection.

Shigella dysentery is less common, and usually human in origin.

Vibrio cholerae/Cholera is rare in Western countries. It is more common in travelers and is usually related to contaminated water (its ultimate source is probably sea water).

Vibrio parahaemolyticus can be found in seafood.

Escherichia coli is a very common cause of diarrhea, especially traveler's diarrhea, but it can be difficult to detect using current technology. The types of E. coli vary from area to area and country to country.

Clostridium difficile is considered the most common cause of infectious diarrhea in hospitalized patients worldwide.[2]

Toxins and food poisoning can cause diarrhea. These include staphylococcal toxin (often from milk products due to an infected wound in workers), and Bacillus cereus.


Worms sometimes cause diarrhea but are often accompanied by weight loss, irritability, rashes or anal itching. The most common is pinworm (mostly a nuisance rather than a severe medical illness). Other worms, such as hookworm, ascaria, and tapeworm are more medically significant and may cause weight loss, anemia, general unwellness and allergy problems.


Giardia lamblia is a common cause.

Amoebic dysentery due to Entamoeba histolytica is an important cause of bloody diarrhea in travelers and also sometimes in western countries.

Another cause is Cryptosporidium, acquired via fecally contaminated food or water.


Percentage of rotavirus tests with positive results, by surveillance week, United States, July 2000--June 2009.

A rotavirus vaccine has between 2000 and 2009 decreased the number of cases of diarrhea due to rotavirus in the United States.[3]


White blood cells in a stool sample (Methylene Blue Stain).

In more severe cases, or where it is important to find the cause of the illness, stool cultures are instituted.

Among medical inpatients, the presence of fecal leukocytes can predict a "breach in the colonic mucosa (any infectious or inflammatory condition, blood in the stool, or acute vascular insufficiency)"[4]:


The first priority in treatment of acute diarrhea is insuring that patients are adequately rehydrated, as significant amounts of fluid may be lost. This fluid loss is the primary mechanism of mortality from acute diarrhea in patients. In moderate to severe cases of acute diarrhea this is often accomplished with saline or another appropriate solution given through an IV line. With mild cases of acute diarrhea, it is often reasonable to reassure a patient, ensure adequate fluid intake, and wait and see. For children in the developing world, the World Health Organization recommends the use of oral rehydration solution and zinc supplementation for treatment of diarrhea.[5]

Parasites (worms and amoeba) should always be treated with antimicrobial drugs.

Antimotility agents

Loperamide can reduce diarrhea in patients with shigella[6], but not in patients with traveler's diarrhea due to enterotoxigenic E. coli.[7]

A systematic review of randomized controlled trials found that loperamide may harm children less than 3 years old.

Antisecretory agents

A randomized controlled trial found that racecadotril, an enkephalinase inhibitor, may reduce the volume of watery diarrhea.[8]


Norfloxacin can reduce the duration of acute diarrhea due to bacterial pathogens.[9] However, norfloxacin may prolong infectivity of patients with salmonella and cause resistant campylobacter.[9]


Acute infectious diarrhea usually lasts 7 days when not treated with antibiotics.[9] It is not uncommon for diarrhea to persist. Diarrhea due to some organisms may persist for years without significant long term illness. More commonly the diarrhea slowly ameliorates but the patient becomes a carrier (harbors the infection without illness). This is often an indication for treatment, especially in food workers or institution workers. In the developing world, infectious diarrhea is a serious, life-threatening illness that results in 4 to 6 million deaths each year, mostly in children.[10]

Salmonella is the most common persistent bacterial organism in humans.


Worldwide rotavirus is the leading cause of severe diarrhea in children under 5.[11]


  1. ^ Infectious Diarrhea.
  2. ^ "Clostridium difficile (C. difficile): Questions and Answers - Public Health Agency of Canada". Retrieved 2007-08-16.  
  3. ^ "".  
  4. ^ Granville LA, Cernoch P, Land GA, Davis JR (2004). "Performance assessment of the fecal leukocyte test for inpatients". J. Clin. Microbiol. 42 (3): 1254–6. doi:10.1128/JCM.42.3.1254-1256.2004. PMID 15004086.  
  5. ^ USAID. Diarrhea Treatment Guidelines For Clinic-based Healthcare Workers: Including new recommendations for the use of ORS and zinc supplementation. 2005.
  6. ^ Murphy GS, Bodhidatta L, Echeverria P, et al. (1993). "Ciprofloxacin and loperamide in the treatment of bacillary dysentery". Ann. Intern. Med. 118 (8): 582–6. PMID 8452323.  
  7. ^ Taylor DN, Sanchez JL, Candler W, Thornton S, McQueen C, Echeverria P (1991). "Treatment of travelers' diarrhea: ciprofloxacin plus loperamide compared with ciprofloxacin alone. A placebo-controlled, randomized trial". Ann. Intern. Med. 114 (9): 731–4. PMID 2012354.  
  8. ^ Salazar-Lindo E, Santisteban-Ponce J, Chea-Woo E, Gutierrez M (2000). "Racecadotril in the treatment of acute watery diarrhea in children". N. Engl. J. Med. 343 (7): 463–7. doi:10.1056/NEJM200008173430703. PMID 10944563.  
  9. ^ a b c Wiström J, Jertborn M, Ekwall E, et al. (1992). "Empiric treatment of acute diarrheal disease with norfloxacin. A randomized, placebo-controlled study. Swedish Study Group". Ann. Intern. Med. 117 (3): 202–8. PMID 1616214.  
  10. ^ World Health Organization. Diarrhoeal Diseases.
  11. ^ "".  

See also

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