Your Health A-Z


'Gastroenteritis' means inflammation of the stomach and intestines.

Alternative names

  • Gastro
  • Gastric ‘flu
  • Diarrhoeal disease
  • Traveller's diarrhoea
  • Food poisoning


An acute infectious syndrome caused by a micro-organism ingested in contaminated food or water, or from other sources. The virus or bacterium affects the stomach lining and intestines, causing some or all of nausea, vomiting, diarrhoea and abdominal cramps, and sometimes more general symptoms such as fever and headache.


Many different viruses may cause gastroenteritis, some examples of which include:

  • rotaviruses (particularly in winter)
  • enteroviruses (more common in summer)
  • adenoviruses, astroviruses, Norwalk virus and other caliciviruses

Gastroenteritis can also be caused by:

  • bacteria – common bacterial causes include Campylobacter, Shigella, Salmonella or certain strains of Escherichia coli. Some bacteria produce toxins which cause “food poisoning”.
  • parasites (Giardia is one example).
  • certain medications.
  • toxins in plants (including mushrooms) or other foods (e.g. “red tide” in shell fish).

As we get older, we develop immunity to the more common viruses and bacteria in our environment, and we are no longer vulnerable to many of them even though we are exposed to them regularly.

These micro-organisms are usually acquired directly or indirectly from another infected person. However, some are present in soil, water and even air. Animals (both livestock and pets) may be a source of infection with certain of the micro-organisms that cause gastroenteritis.

In the face of ongoing gastro-intestinal symptoms in a child one would consider dietary causes such as lactose intolerance (intolerance of milk sugar).

Who gets it and who is at risk?

Anyone can get gastroenteritis. In fact no child will escape an episode or two of gastroenteritis however good their socio-economic circumstances. However, certain groups are more vulnerable.

  • Babies and young children, whose immune systems are still developing.
  • Old people whose immune systems are weakened.
  • The factors that allow gastroenteritis to spread commonly exist in impoverished communities that have bad sanitation and poor food storage facilities. Gastroenteritis is more dangerous if nutrition is poor. Gastroenteritis is particularly prevalent in the impoverished communities. It is a primary cause of death in babies and young children in African countries.
  • The incidence of gastroenteritis is increased by immunodeficiency diseases such as AIDS.
  • Travellers who come into contact with local bacteria and viruses against which their immune systems do not have pre-existing defences.

Misunderstood causes

The germs that cause gastroenteritis usually enter your system through your mouth. There is an incubation period of a few hours to a few days before the illness becomes apparent.

Because infection may occur a while before people become symptomatic (appear sick), people who contract gastroenteritis often incorrectly assume that the last meal they ate gave them food poisoning. This may be the case, however, there is no way to prove it without analysing the food itself.

Symptoms and signs

Typical symptoms include:

  • Nausea and/or vomiting.
  • Diarrhoea. Diarrhoea is the frequent passing of very runny stools. Viral diarrhoea is watery. Bacterial diarrhoea can be very smelly, and contains mucus and visible blood. If blood and pus is present in the diarrhoea it is termed “dysentery”.
  • Abdominal pain and cramps.
  • Fever.
  • Other general symptoms of being unwell, such as headache.

“Upper” gastrointestinal symptoms (nausea and vomiting, abdominal pain) can be dominant with some causes of gastroenteritis e.g. Staphylococcal food poisoning and “lower” gastrointestinal symptoms (diarrhoea) with others e.g. cholera. However, a variable mix of upper and lower gastrointestinal symptoms occurs with many causes of gastroenteritis eg. rotavirus.

Dehydration is an important sign of advanced and possibly untreated gastroenteritis. Symptoms of serious dehydration include:

  • Dry mucous membranes in the mouth
  • Loss of the normal elasticity of the skin
  • In babies, sunken eyes or sunken fontanelle (the fontanelle is the soft spot at the top of a baby's head)
  • Fast breathing
  • A drop in urine output
  • Weight loss over days or even hours
  • Listlessness or lethargy


Diagnosis is usually carried out based on symptoms and medical examination of the patient. It is not essential to know exactly which virus or bacteria caused the condition as treatment using specific drugs is rare (see “treatment”). However, it can be useful to ask whether the patient has been in contact with others with symptoms who may have passed on a particular micro-organism, or whether they have exposed themselves to any other common risk factors. Recent travel can also be a clue as to the cause.

Laboratory testing of stools can be quickly carried out in children to determine whether the gastroenteritis is caused by rotavirus. Tests to determine other viruses as causes are not routinely used – they are both unnecessary and unlikely to significantly affect how the patient is treated.

In cases of dysentery, a fresh stool specimen may be examined under the microscope for parasites such as Entamoeba histolytica (the cause of amoebic dysentery), and bacterial cultures may be done to identify the culprit.


The micro-organisms that cause gastroenteritis are many and varied, and new strains can emerge from year to year, making it difficult to inoculate people against gastroenteritis. Rotavirus is the single leading cause of fatal diarrhoea in children, and a fairly successful vaccine was recently developed against it. However, the rotavirus vaccine has been withdrawn from use in the countries that had begun to use it, while a possible side-effect of the vaccine is investigated.

It is not possible to physically isolate yourself sufficiently to prevent any contact with the micro-organisms that cause gastroenteritis. However, if your immune system is healthy, you may develop immunity to many of them after a first exposure, without even getting serious symptoms. Some micro-organisms will cause gastroenteritis during a first infection, but subsequent infections will not cause symptoms.

Infection through contact with infected people can be prevented to some extent by avoiding contact with the bodily fluids of infected people and:

  • frequently cleaning and disinfecting high-risk surfaces, such as food preparation areas and toddlers’ toys
  • encouraging those who have symptoms of gastroenteritis to practise good hygiene e.g. hand washing after using the toilet
  • washing hands after going to the toilet or changing nappies, working with soil, or playing with pets
  • washing your hands before preparing food, between handling raw and ready to eat foods, and before eating

Risks of environmental contamination due to poor living conditions or bad sanitation can be reduced by:

  • breast-feeding babies: this avoids the risks of contaminated water and unsterile bottles and teats.
  • practising good food storage techniques. Raw foods such as meat, poultry, fish, and eggs must be eaten within a limited time period if storage at a cool temperature is not possible. (Cool temperatures prevent bacterial growth). These foods should be stored separately so as not to contaminate other foodstuffs.
  • thoroughly cooking all food to kill any bacteria and allowing microwaved food to stand for the specified period after cooking.
  • peeling fruit and vegetables and thoroughly washing those that cannot be peeled when there is a risk of contamination from human or animal manure.
  • reheating previously cooked food to at least 75 degrees C.
  • boiling drinking water for a few minutes if water supplies are not reliably filtered and chlorinated.
  • keeping insects and animals away from food preparation areas.

In many impoverished areas, only overall improvements in the standard of living, sanitation and other environmental factors can really help reduce incidence of gastroenteritis and other “diseases of poverty”.


Patient care is much the same no matter what causes gastroenteritis. Most cases of gastroenteritis get better without any specific treatment.

The most important aspect of treatment is to maintain hydration.

Rehydration can usually be done at home. An oral rehydration solution should be used rather than plain water in large amounts. This is because plain water is not absorbed as well as water that contains sugar and salt, and because dehydration also results in the loss of salts that need to be replaced to avoid unbalancing the salt and pH (acid balance) in your system.

Rehydration solutions are available from pharmacies. You can mix your own solution using the following ingredients:

  • ½ level (5ml) teaspoon salt
  • 8 level (5ml) teaspoons sugar

Dissolve in 1 litre of clean boiled water.

Consult with your doctor to ensure that ingredients are not dangerous to the health of the patient before mixing any solutions yourself.

In babies with mild gastroenteritis, continue with normal milk feeds along with rehydration fluids by cup or bottle.

In adults, fruit juice, bottled drinks such as lemonade, rooibos tea and home-made clear soups are suitable. Caffeine-containing drinks should be avoided.

If vomiting results from rehydration attempts, try giving liquids in smaller quantities (as little as a teaspoon at a time) at intervals of fifteen minutes or more, and increase intake gradually. Try to at least match urine output (or other fluid loss) with fluid intake to ensure that rehydration succeeds.

Start a normal diet once the patient's symptoms settle.

If the cause of the gastroenteritis can be established as bacterial then antibiotic medicines may help treat the disease; however, as it is difficult to determine the causes of gastroenteritis it is seldom advisable to treat it with antibiotics. Some antibiotics can cause or even worsen diarrhoea, making prescribing them for this condition even riskier.

Other medications

  • There is no evidence that adsorbents such as chalk and kaolin mixtures are effective for “binding” diarrhoea.
  • Medications that reduce gut contractions, such as diphenoxylate (Lomotil) or loperamide (Imodium), can be useful to control diarrhoea in adults but should only be used for a limited time. These sorts of medications should not be used in young children.

Try to give education and intervene where possible to improve the patient's environment in order to avoid worsening gastroenteritis, reinfection or infection of others living near them.

Outcome of treatment

Mild cases of gastroenteritis will settle within days and require only attention to hydration. More severe cases require active management.

When to call the doctor

Call a doctor or take the patient to a clinic if:

  • They haven't urinated for six hours or more
  • They are unable to take or keep down even clear liquids
  • They are becoming listless or lethargic
  • Their mouth is persistently dry or their eyes are becoming sunken (this is particularly common in children who are dehydrated)
  • There is any sign of bleeding from the gut.

If needed, a doctor will give fluids intravenously until the vomiting and diarrhoea resolve.

In very severe cases where the patient is shocked through loss of fluids, admission to an intensive care unit may be required.

Reviewed by Dr Eftyhia Vardas, University of the Witwatersrand, Dr John D. Burgess, Red Cross Children's Hospital

The information provided in this article was correct at the time of publishing. At Mediclinic we endeavour to provide our patients and readers with accurate and reliable information, which is why we continually review and update our content. However, due to the dynamic nature of clinical information and medicine, some information may from time to time become outdated prior to revision.