Main source: eMedicine Health's "Gastroenteritis"


Gastroenteritis is a bowel infection causing diarrhea and sometimes vomiting. Vomiting may settle quickly, but diarrhea may last up to 10 days. In most cases medicine is not needed, however babies can become sick very quickly because they lose fluids. Gastroenteritis is often also called "food poisoning", "gastro" or "stomach flu".


Gastroenteritis may be caused by many pathogens, but is most often caused by either viruses or bacteria. Viruses and bacteria are very contagious and can spread through food or water. In upto 50% of diarrhoea cases, no specific agent is found. Not washing your hands after defecating can spread the disease from person to person.

Gastroenteritis caused by viruses can last 1-2 days. Gastroenteritis caused by bacteria can last one week or more.


- Escherichia coli - Traveler’s diarrhea, food poisoning, dysentery, colitis, or uremic syndrome

- Salmonella - Typhoid Fever; handling poultry or reptiles such as turtles that carry the germs

- Campylobacter - Undercooked meat, unpasteurized milk

- Shigella - Dysentery


Viral outbreaks (30-40% of cases in children) can spread rapidly through close contact among children in day care and schools. Poor handwashing habits can spread viruses. Common viral causes include the following:

- Adenoviruses

- Rotaviruses: Rotaviruses are the most common cause of severe diarrhoea in children, killing about 600,000 children in developing countries (as of 2005). However, new vaccines have proven to be safe and effective.

- Caliciviruses

- Astroviruses

- Norovirus (formerly called Norwalk-like virus or NLV) and Norwalk virus. Norovirus was attributed to 9 out of the 21 outbreaks of acute gastroenteritis on cruise ships reported to the CDC’s Vessel Sanitation Program from January 1, 2002, to December 2, 2002. Noroviruses cause about 23 million cases of acute gastroenteritis each year and are the leading cause of outbreaks. It is transmitted fecal-orally. It is estimated that Norwalk viruses are responsible for about 1/3 of the gastroenteritis cases not involving the 6-to-24-month age group.

Parasites and Protozoans:

These tiny organisms are less frequently responsible for intestinal irritation. You may pick up one of these by drinking contaminated water. Swimming pools are common places to come in contact with these parasites. Common parasites include:

Giardia - The most frequent cause of waterborne diarrhea causing giardiasis

Cryptosporidium - Affects mostly people with weakened immune systems, causes watery diarrhea

Other Causes:

Chemical toxins most often found in seafood, food allergies, heavy metals, antibiotics, and other medications also may be responsible for bouts of gastroenteritis that are not infectious to others.

- Medications (Aspirin, Nonsteroidal anti-inflammatory medicines such as Motrin or Advil, Antibiotics, Caffeine, Steroids - Excessive use or a sudden change in frequency or dosage, Laxatives,

- Inability to tolerate the sugar lactose in milk and milk products such as cheese and ice cream

- Exposure to heavy metals sometimes present in drinking water (Arsenic, Lead, Mercury)


Gastroenteritis may affect both the stomach and the intestines, resulting in one or more of the following symptoms:

Common symptoms:

- Low grade fever (99°F)
- Nausea with or without vomiting
- Mild-to-moderate diarrhea: May range from 2-4 loose stools per day for adolescents and adults to stools that run out of the diaper in infants.
- Crampy painful bloating
- Vomiting: May or may not accompany diarrhea. If you do vomit, your dehydration rate will increase. Either together or alone, diarrhea and vomiting result not only in loss of significant amounts of fluid, leading to dehydration and possibly shock, but also loss of potassium, sodium, and bicarbonate.

More serious symptoms

Blood in vomit or stool
Vomiting more than 48 hours
Fever higher than 101°F
Swollen abdomen or abdominal pain coming from the right lower side
Dehydration - Little to no urination, extreme thirst, lack of tears, and dry mouth (dry diapers in infants)

In general, symptoms caused by bacteria or their toxins will become apparent after the following amount of time:
- Staphylococcus aureus in 3-6 hours
- Clostridium 8-10 hours
- Salmonella in 12-72 hours

Going to the Doctor

If a patient with gastroenteritis is losing too much fluid from vomiting and diarrhoea and is unable to keep liquids in, they should consult a doctor. If there is blood in the feces, vomiting that lasts more than 48 hours, a very high fever, swollen stomach or dehydration (little urination, extreme thirst, lack of tears, dry mouth), then they must consult the Emergency Department.

A doctor first will determine if your symptoms are acute (lasting less than 2 weeks) or chronic (longer lasting). A long-lasting illness suggests an inflammation or immune disorder, which should be checked after infection has been ruled out. Sudden onset of illness may indicate changes in diet or medication.

A doctor will then try to make out whether it is a virus or a bacteria causing the symptoms.

Signs for bacterial infection: rapidly developing fever, abdominal pain, bloody stool and presence of white blood cells (leukocytes).

Signs for viral infection: watery stools without blood or leukocytes are more typical of viral- or toxin-induced diarrhea.

The doctor will then:
- Ask typical questions (how long? what type? alleviating/aggrevating factors? weight loss?)
- Check for an outbreak (any other family members/friends affected?)
- Check for inflammation (of appendix, gallbladder, pancreas)
- Lab tests (check feces for blood, mucus or odor, maybe even for parasites and their eggs)
- Travel history (Mexico = E coli)
- Exposure to poisons or irritants (contaminated water = Giardia)
- Diet change
- Medication (antibiotic irritation perhaps)


Because dehydration is the big problem with gastro, patients should get adequate amounts of fluid. Children and infants, in particular, are prone to lose a lot of fluid very fast so they must be given a careful watch (for infants, breastfeeding is the best solution to dehydration).

First line of treatment is to provide proper hydration. It is not just water that has been lost, but also important electrolytes such as potassium and sodium. Drinking water will not be enough (in fact it may just dilute the electrolytes). Tea, fruit juices and soft drinks are no-no's. There's a common myth that soft drinks such as lemonade will heal dehydration, but those drinks contain too much sugar and not enought electrolytes. An appropriate choice of drink would be an Oral Rehydration Solution (such as Pedialyte, Rehydrate, Resol, and Rice-Lyte) available at any pharmacy. After a liquid diet, move on to solid foods.

*ORS (oral rehydration solution): simple, cheap and effective for diarrhea-related dehydration, due to cholera or rotavirus. Consists of salts and other substances – glucose, sucrose, citrates. 90 mm Glucose, 60 mm Sodium, and amounts of potassium, chloride and citrate. Soft drinks like lemonade are bad myths for dehydration (although best one is sprite, but still bad. Dilute if must, takes away sugar. Pepsi is horrible).

*You can also make your own oral rehydration solution at home. The World Health Organization has established a field recipe for fluid rehydration: Mix 2 tablespoons of sugar (or honey) with ¼ teaspoon of table salt and ¼ teaspoon of baking soda. (Baking soda may be substituted with ¼ teaspoon of table salt.) Mix in 1 liter (1 qt) of clean or previously boiled water.

Medical line of treatment: Upon seeking medical attention, if you cannot take fluids by mouth because of vomiting, the doctor may insert an IV to put fluid back into your body (rehydration). With severe symptoms, a surgeon, toxicologist, gastroenterologist, or other specialist may see you.

Pathogenic line of treatment: But what about the pathogen! Aren't we making the classic mistake of "treating the symptoms and not the disease"? Well, in gastro- cases, usually the body's defence system is able to fight the disease quicker than doctors can specify it. Therefore, supplying hydration is really all that's necessary.

Doctors usually don’t give antibiotics until bacteria have been identified. Antibiotics may be given for certain bacteria, specifically Campylobacter, Shigella, and Vibrio cholerae, if properly identified through laboratory testing. Otherwise, using any antibiotic or the wrong antibiotic can worsen some infections or make them last longer.

For adults, the doctor may give medications to stop vomiting (which are called antiemetics. Doctors usually do not recommend antiemetics for children. A single dose of Compazine may be prescribed, however, for children older than 2 years. Doctors generally avoid antidiarrheal medications for all age groups.

Final Words

Diarrhea is one of the leading causes of infant sickness. Worldwide, diarrhea accounts for 3-5 million deaths for all age groups. In general, most adults and children recover after they are appropriately rehydrated.

Vaccinations for Salmonella typhi, Vibrio cholerae, and rotavirus have been developed, but doctors generally give them out based on your medical and travel history. If you are travelling to a third world country, then maybe consider one.

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