What is gastroenteritis?

Gastroenteritis, also known as gastro, is a condition causing inflammation of the lining of your large and small intestines and also your stomach. It can cause fever, vomiting, cramps and diarrhoea. Gastroenteritis is usually highly contagious and can be contracted by eating food or drinking water that has been contaminated by viruses, bacteria or parasites, through contact with other infected people or through the faecal-oral route. Due to its usually highly-contagious nature, gastroenteritis can quickly spread through communities where close contact is inevitable, such as schools or nursing homes. You can also develop gastroenteritis by ingesting certain medications or chemical toxins. Healthy individuals usually recover from gastroenteritis without any medical intervention, but it can prove fatal to the elderly, frail or very young children. It is the main cause of diarrhoea for both adults and children worldwide.


Infectious gastroenteritis is usually caused by viruses, bacteria or parasites. The most common way to become infected is by consuming contaminated food or water, or via the faecal-oral route, which involves contact with the faecal matter of an infected person that is transferred to the mouth. With infectious agents, such as bacteria or viruses, the invading germs cause the lining of the intestines to become inflamed and irritated. This inflammation stops water being absorbed and causes watery stools.


Viruses that can cause gastroenteritis include:

  • Norovirus - symptoms can be severe and the infection is usually caused by ingesting contaminated water or food. Oysters and other uncooked seafood are a common source. Particles containing virus can also become airborne during vomiting and contaminate local surfaces. Symptoms appear after 12-48 hours of infection and can last up to three days;
  • Rotavirus - highly contagious, it can cause severe, dehydrating diarrhoea in young children and babies, often resulting in hospital admission. The infection is usually spread child-to-child, by faecal-oral transmission;
  • Adenovirus - this highly contagious virus commonly affects children under two years of age. Symptoms can also include sore throat, conjunctivitis and respiratory infection, but these are rarely serious. Spread is via physical contact, sneezing and the faecal-oral route, and;
  • Astrovirus - this is a common cause of gastroenteritis in young children, with less severe effects in adults. It is usually spread by faecal-oral transmission and by eating contaminated foods. Being highly contagious, astrovirus is a common cause of gastroenteritis in schools, childcare centres, or close communities.


Bacteria usually find their way into your body via contaminated food or drinks that have been handled by unwashed hands. Common bacterial infections known to cause gastroenteritis are:

  • Escherichia coli (E. coli) - this strain of bacteria is the most common cause of gastroenteritis caught while travelling through developing nations (traveller's diarrhoea). It is caused by faecal contamination in water and food and through poor sanitary habits. It will only affect those who have not built up immunity to it;
  • Salmonella, Staphylococcus aureus and Cholera bacteria - these are common bacteria that lead to diarrhoea. Infection is spread through poor hygiene, contact with animal faeces or eating contaminated foods, and; 
  • Campylobacter and Shigella - these types of bacteria are often found in animal faeces and cause diarrhoea. Infection is caused by actions such as consuming contaminated food or water, eating undercooked meat, especially chicken, and not washing your hands after handling infected animals.


Intestinal parasites such as Giardia lamblia, Entamoeba histolytica and Cryptosporidium can cause gastroenteritis with nausea, watery diarrhoea and severe cramping. Poor handwashing, contact with animals and contaminated food are the usual modes of infection.

Chemicals and toxins

Ingesting water or foods tainted by heavy metals such as lead, mercury, cadmium or arsenic and also ingestion of a range of plant, animal and chemical toxins can cause gastroenteritis.


Certain medications, such as magnesium-containing antacids, antibiotics, antiparasitic medication, laxatives and chemotherapy medication can cause gastroenteritis. Your doctor may recommend ceasing your medication temporarily or permanently, depending on the severity of your symptoms.


Chemical substances that kill or suppress the growth of bacteria.


A medication-based treatment, usually used in the treatment of cancers. There are numerous, different types of chemotherapy drugs that can be prescribed by a specialist. These can commonly be used alongside other cancer treatments such as surgery and radiotherapy.

Risk factors

Gastroenteritis can affect you at any age, no matter where you are from, but the following factors can heighten your risk of being infected:


Young children and babies are highly susceptible to gastroenteritis, as their immune systems are not fully developed. The elderly, especially those living in care homes, are also at greater risk of infection due to close proximity to others. 

Communal or public places

You are at much greater risk of being infected with gastroenteritis if you are in close contact with other people on a daily basis.

Weakened immunity

You are at greater risk if you have a weakened immune system due to ongoing illness, stroke, heart disease, chemotherapy, HIV/AIDS or medications that cause an immune deficiency.

Poor hygiene

Poor hygiene and unsanitary food-handling methods make it easy for a wide range of microorganisms to make their way into the food chain. Bacteria from an infected person's stool can easily be passed to others if they do not wash their hands properly after using the bathroom. If they were to go swimming or touch objects such as communal doorhandles, they could infect numerous people without being aware of it. 

Travel to developing nations

Many travellers experience gastroenteritis while travelling through developing nations, where sanitation and food hygiene standards may be poor. Infectious agents may be present in drinking water, food and in communal areas such as bathrooms.


A medication-based treatment, usually used in the treatment of cancers. There are numerous, different types of chemotherapy drugs that can be prescribed by a specialist. These can commonly be used alongside other cancer treatments such as surgery and radiotherapy.

Immune deficiency

A condition in which the immune system does not function adequately and cannot properly protect the body from infection.

Immune system

The organs and cells involved in protecting the body against infection.

Signs and symptoms

Signs and symptoms of gastroenteritis include:

  • Diarrhoea - usually quite watery - which may contain pus, mucus or blood in more severe cases;
  • Stomach cramps with bloating, loss of appetite, nausea and vomiting;
  • Muscle aches and generalised tiredness, and;
  • Low-grade fever and sometimes headache.

Gastroenteritis can cause stomach cramps and nausea. 


A thick, viscous liquid that is secreted for lubrication and to form a protective lining over certain tissues.


A bodily fluid that is the result of an inflammatory response at an infection site. Its colour can range from whitish to yellow to green, depending on the composition. Pus is mainly composed of dead bacteria, white blood cells and cellular debris.

Methods for diagnosis

While the majority of cases go undiagnosed, your doctor may suggest the following to discover what is causing your gastroenteritis:

Faeces microscopy culture and sensitivity

A stool test used to check if there is a disease-causing organism or virus in the digestive tract with the added benefit of finding which medications would be most useful in targeting that organism or virus.

Types of treatment

The majority of cases of gastroenteritis are advised to stay at home and rest, with no medical treatment offered. Laboratory-diagnosed parasites and some types of infectious bacteria will require medication. In some cases medication can also be used to help stop severe vomiting. Avoiding dehydration is the main priority, especially in very young children, the elderly or frail individuals. Hospitalisation for dehydration is not uncommon and will involve insertion of an intravenous (IV) drip to get fluids back into your system.

Home care

With home-care regimes, the following advice may be given:

  • Avoid solid foods until all vomiting stops;
  • Have complete bed rest to conserve your energy;
  • Avoid close contact with others, as you may infect them too;
  • Wash your hands thoroughly with soap after going to the toilet;
  • Take small sips of clear liquids to stay hydrated - try clear broth and non-carbonated drinks;
  • Take oral rehydration drinks to help replace lost fluids;
  • Avoid caffeine and alcohol;
  • Avoid spicy or greasy foods and dairy products and start by eating bland foods once your symptoms have calmed down;
  • Avoid medications unless prescribed by your doctor, as they may cause further stomach upsets, and;
  • Avoid taking antibiotics, antidiarrhoeal medications or antiemetics (they can keep infections in your system and delay recovery), unless prescribed by your doctor.

Gastroenteritis can cause exhaustion, bed rest is essential.Bed rest and staying hydrated are essential during gastroenteritis. 


Chemical substances that kill or suppress the growth of bacteria.


The majority of cases of gastroenteritis do not require medication. Depending on the type of gastroenteritis diagnosed, your doctor may prescribe one of the following:

  • Antiparasitic drugs;
  • Antibiotics;
  • Antiviral drugs (rarely);
  • Antiemetic (anti-nausea) drugs, or;
  • Antidiarrhoeal drugs.


Chemical substances that kill or suppress the growth of bacteria.

Potential complications

The main complications of gastroenteritis come from losing fluids (dehydration), which can quickly become life-threatening to small children and babies. If you are over 60 years of age, or have a cardiovascular condition such as heart disease, or a history of stroke, you can also become seriously ill after relatively short periods of diarrhoea.

Other complications may include:

  • Malnutrition (lack of nutrition), which leads to weakness;
  • Dehydration (lack of water in your body). In children, watch for sunken eyes, lack of energy, dizziness, dry skin and lack of tears or urine;
  • Anaemia (low levels of red blood cells) and a pale, exhausted appearance;
  • Electrolyte imbalance (mostly salt and sugar), and; 
  • Haemolytic uremic syndrome (HUS) caused by E. coli - this is a very rare condition that affects young children. If your child has blood in their diarrhoea, get medical attention immediately.


Substances that form ions when dissolved in water. These include potassium and sodium minerals that are necessary for normal functioning of the body and all its cells.


Gastroenteritis is usually a short-term condition that doesn't tend to be serious for healthy adults, but can be serious and even fatal for less robust individuals. The amount of liquids lost during an episode can lead to severe dehydration, which can be life-threatening if you have a weakened immune system, are a young child or are elderly. 

Immune system

The organs and cells involved in protecting the body against infection.


Hygiene is probably one of the most important factors in preventing gastroenteritis. Simple measures to ensure good hygiene include:

  • Washing your hands thoroughly with soap and water after handling animals, gardening, changing nappies, going to the toilet, smoking, cleaning up infected vomit or faecal matter, sneezing or handling raw foods; 
  • Ensuring raw and cooked foods are not handled with the same utensils or allowed to come into contact with each other;
  • Ensuring cold foods are kept under 5°C and hot foods are kept above 60°C to avoid bacterial growth;
  • Ensuring all foods are well cooked, especially meat and seafood;
  • Replacing cloth towels with paper towels;
  • Ensuring all kitchen surfaces are kept clean and not allowing family pets to access food preparation areas;
  • Washing all toys and equipment that infected children have been in contact with;
  • Keeping your bathroom clean, especially the toilet and any handles or taps that are constantly touched;
  • Keeping babies' changing mats clean by wiping with disinfectant after each use;
  • When travelling to developing nations, only using bottled water (even for brushing teeth), not having ice in drinks, avoiding uncooked foods, food buffets and already-peeled fruits and vegetables, and;
  • Not swimming in water used by animals or, if you do, keeping your head above water to avoid swallowing water.

Wash hands thoroughly after using the bathroom, handling food and changing nappies.Frequent and thorough handwashing with soap can prevent gastroenteritis.