Causes of Watery Diarrhea

The World Health Organization, WHO, defines diarrhea as 3 or more loose stools per day 6. It is estimated that American adults suffer 99 million episodes of diarrhea each year, leading to greater than 250,000 hospitalizations (see ref 1 and also 2, 5, 6 and 7) ). While in children under 5 years of age, diarrheal illnesses are the second leading cause of death worldwide. (see ref 6). Diarrhea that lasts only up to fourteen days is termed acute, while diarrhea that lasts longer than a month is defined as chronic 1. (see ref 1, 5, 6 and 7). Watery diarrhea is the gastroenteritis, or inflammation of the stomach or intestines, symptom defined by stool that is more liquid in consistency and without blood. It can be caused by viruses, bacterial infections, parasites or a variety of noninfectious conditions. (see ref 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10).

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If you are experiencing serious medical symptoms, seek emergency treatment immediately.


The most common causes of diarrhea in the United States are viruses, such as rotavirus, astrovirus, adenovirus and norovirus or Norwalk virus. (see ref 1 and 5). While the rotavirus is the leading diarrheal illness in children, the most common cause of viral gastroenteritis in adults is the norovirus according to the Centers for Disease Control and Prevention or CDC 238. (see ref 9 and 10). In fact the norovirus is considered the leading cause of food poisoning in the U.S. (see ref 9). The norovirus symptoms include fever, vomiting and stomach pain along with diarrhea. (see ref 9). Typically a person develops symptoms 12 to 48 hours after exposure to these viruses. Most people recover within 24 to 72 hours. (see ref 9). These viral infections spread through contaminated food, water, and surfaces. The best way to prevent the spread of these diseases is by washing one's hands before preparing, eating or handling food and after changing diapers and using the toilet. The norovirus, for instance, is notoriously resistant to hand sanitizers and to temperatures up to 140 degrees Fahrenheit, so washing hands with soap and water is essential to prevent spreading. (see ref 9 and 10).

Bacterial Infections

The Cleveland Clinic explains that the most common for of bacterial watery diarrhea is traveler's diarrhea, which is caused by enterotoxigenic Escherichia coli or ETEC, followed by Bacillus cereus and Staphylococcus aureus 1. (see also ref 5) Due to the prevalence of these bacterial infections abroad, the CDC developed the simple recommendations for travelers of "boil it, cook it, peel it, or forget it." (see ref 4). Yet despite these numbers, only 1-6% of all stool cultures in the people with watery diarrhea in the U.S. reveal bacterial infections. (see ref 7, p.1). Outside of the U.S. on the other hand, bacterial infections are quite prevalent. (see ref 6). Although ETEC is the most common bacterial infection worldwide, the bacteria Vibrio cholerae has been implicated in many significant pandemics, resulting in over millions of diarrheal cases and several thousands of deaths in developing countries. (see ref 7, p. 2 and ref 6). The treatment for bacterial infections consists of antibiotics and the maintenance of fluid and electrolytes through significant and constant rehydration with safe drinking water. (see ref 2 and 6).


Parasitic diarrheal infections are unlike viral or bacterial illnesses, largely due to the fact that they can be present for months or years, while bacterial and viral illness last less than two weeks. (see ref 4) An article published in "Gut Microbes" in January 2010 indicates that Giardia lamblia is the most prevalent intestinal parasite cause of diarrhea worldwide 4. It is a non-invasive organism called a protozoan that collects in the upper portion of the small intestine by sticking to the mucosal lining in the gut. It causes both an acute and chronic diarrhea that is characterized by abdominal pain and the prevention of nutrient absorption, leading to a person's malnutrition 1. (see ref 4). Another parasitic condition is Entamoeba histolytica which causes a condition known as amebiasis. (see ref 4). This is an inflammatory parasite that produces an ulceration of the intestines as well as a watery diarrhea. Both of these conditions can be treated by medications. (see ref 4).

Noninfectious Causes

Noninfectious causes include inflammatory conditions, food allergies or intolerances and medication side effects. According to the American College of Gastroenterology, or ACG, one of the most common adverse effects of pharmaceutical drugs is a watery diarrhea 5. This form of diarrhea typically stops after the offending medication has been discontinued. (see ref 1 and 5). On the other hand, inflammatory conditions can cause a chronic watery diarrhea. These include inflammatory bowel disease--which is an inflammation of the intestinal lining, Celiac Sprue--an autoimmune allergy to gluten products, and chronic pancreatitis--and inflammation of the pancreas, and they are all characterized by malabsorption or impaired digestion of fats and vitamins and lead to malnutrition. (ref 1 and 5). Other noninfectious causes are related to the body's response to certain foods such as is the case when ingesting sorbitol or other indigestible sugars, as reported by the ACG. Problems with digestion of dairy products also occur namely lactose intolerance. These type of food allergies are typically more prevalent in African-Americans and Asian-Americans. (see ref 1 and 5)


If a person experiences any of the aforementioned symptoms, it is best to contact his or her healthcare provider as soon as is possible.