User:Diberri/Infectious diarrhea

Infectious diarrhea is diarrhea caused by an infection of the digestive system, either by a bacterium, virus, or parasite. The most common causative organisms are viral, and of these, norovirus predominates. The clinical course of infectious diarrhea is marked by watery, sometimes bloody, stools. In healthy individuals, most cases are self-limiting and resolve within two weeks.

Because the illness is generally self-limited, treatment is usually supportive, and consists of administration of fluids and nutrition. At the center of treatment is oral rehydration therapy.

Epidemiology
Infectious diarrhea is a significant concern for global health. It is a major medical illness worldwide, accounting for _____ hospitalizations and _____ deaths annually. In 2005, it caused 18% of deaths worldwide in children under the age of five years old. All individuals can be affected, regardless of age, gender, race, or socioeconomic status. It can be particularly worrisome in young, elderly, malnourished, or immunocompromised individuals.

Types

 * Traveler's diarrhea
 * Dysentery

Causes
Microorganisms by definition are the cause of infectious diarrhea, although rarely are patients diagnosed with a particular causative organism. Worldwide, the most common causes of infectious diarrhea are ____, ____, and ____. In industrialized nations, the most common causes are viral, and of these, norovirus predominates. Bacteria cause the majority of the remainder of

Infectious diarrhea is by definition caused by a microorganism, although rarely are patients diagnosed with a causative organism. Among hospitalized patients, the most common cause of infectious diarrhea is _____, whereas _____ is responsible for the majority of cases in outpatients.

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

Virus
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 can also cause these symptoms.

Bacteria/toxins/protozoans
Common organisms include Campylobacter (from animal products), Salmonella (also often from animal foodstuffs), and Cryptosporidium (ditto), and (lives in water).

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

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). 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.

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. Often "food poisoning" is really Salmonella infection.

Giardia lamblia is a common cause.

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

Risk factors

 * Immunocompromise (HIV/AIDS, etc.)
 * Young, elderly
 * Malnutrition
 * Low SES
 * Poor hygiene
 * Hospitalization
 * Day care

Signs and symptoms
Diarrhea is marked by loose motion watery and mucoid secretion

Diagnosis
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)" :
 * sensitivity = 28%
 * specificity = 92%

Treatment
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.

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

Antimotility agents
Loperamide can reduce diarrhea in patients with shigella, but not in patients with traveler's diarrhea due to enterotoxigenic E. coli.

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.

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

Prognosis
Acute infectious diarrhea usually lasts 7 days when not treated with antibiotics. 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.

Salmonella is the most common persistent bacterial organism in humans.