Gastroenteritis is an inflammation of the gastrointestinal tract (the pathway responsible for digestion that includes the mouth, esophagus, stomach, and intestines). Gastroenteritis is also sometimes referred to as "stomach flu," even though it is not related to influenza.
Gastroenteritis is a contagious disease that occurs due to inflammation and irritation in the lining of the abdomen and intestine. Gastroenteritis leads to heavy loss of fluids, due to the presence of certain viruses and bacteria in the body. In most cases, gastroenteritis gets cured within 2 - 3 days, with minimal treatment. However, it can turn into a life-threatening disease, especially for infants, young children and old people, because they have weak immune systems.
Gastroenteritis is an infection of the stomach and intestines (bowel). The infection interferes with one of the main functions of the intestines, which is the absorption of water from the contents of your intestines and into the body.
This is the reason why the most common symptom of gastroenteritis is watery diarrhoea, and why dehydration is such a common complication.
The most two common causes of gastroenteritis in adults in England are:
a norovirus infection
food poisoning caused by bacteria
Noroviruses are the most common cause of viral gastroenteritis in adults. Norovirus infections are sometimes called 'winter vomiting disease' because people tend to get them during the winter months. However, norovirus infections can occur at any time of the year.
Norovirus outbreaks are common, particularly within contained environments such as hospitals, nursing homes, schools and cruise ships. This is because the illness spreads very easily from person to person, and the virus can survive for several days in a contaminated area.
Noroviruses can be spread through contact with an infected person, through contact with contaminated surfaces or objects, or by eating or drinking contaminated food or water.
There are many different types of norovirus, and it is possible for a norovirus infection to occur several times. This is because after getting the illness, immunity to the virus only lasts for 14 weeks.
Most cases of bacterial gastroenteritis are caused by food poisoning.
Some cases of viral gastroenteritis are also caused by food poisoning. Food can be contaminated with a virus if handled by a person with a viral infection.
Food can become contaminated at any stage during its production, processing or cooking. For example, it can be caused by:
not cooking food at the right temperature and/or for the right length of time
not chilling food at the correct temperature
the food being handled by someone who has not washed their hands properly
people eating food after it has passed its ‘use by’ date
cross-contamination
Cross-contamination is a cause of food poisoning that is often overlooked. It occurs when harmful bacteria are spread between food, surfaces and equipment.
For example, if you prepare raw chicken on a chopping board and then do not wash the board before preparing a ready-to-eat meal such as a salad or sandwiches, harmful bacteria can be spread from the chopping board to the ready-to-eat meal.
Cross-contamination can also occur if you store raw meat above ready-to-eat meals. The meat juices can drip onto the meals and contaminate them.
The most common types of bacteria associated with gastroenteritis are:
campylobacter – a bacterium found in raw meat and poultry, unpasteurised milk and untreated water
salmonella – a bacterium found in raw meat, poultry, eggs and unpasteurised milk
escherichia coli (E. coli) – a bacterium found in undercooked beef and unpasteurised milk
Travellers’ diarrhoea is a term used to refer to gastroenteritis that is acquired when travelling abroad. Travellers’ diarrhoea can be caused by a range of different bacteria or parasites such as:
the shigella bacterium or the entamoeba parasite, which are both spread through poor hygiene and cause a type of travellers’ diarrhoea known as dysentery
cryptosporidium, which is a parasite found in soil, food or water that has been contaminated with animal or human faeces
giardia intestinalis, which is a parasite found in water that has been contaminated with animal or human faeces (infections caused by this parasite are known as giardiasis)
The symptoms of gastroenteritis are:
diarrhea,
nausea,
abdominal cramps, and
vomiting.
Not all affected individuals will develop all symptoms. Some people also may develop a mild fever of about 100 F (37.7 C). Most symptoms will resolve in about 2 to 5 days. Gastroenteritis may cause dehydration during this short time period, mainly in children or debilitated adults. In this article, gastroenteritis with dehydration is considered severe gastroenteritis.
People with symptoms of diarrhea, bloody diarrhea, nausea, or vomiting that last longer than 5 days, and often may have additional symptoms of fever (greater than 101 F, 38.3 C), malaise, dehydration, sepsis, or additional symptoms, for this article, will not be considered to have gastroenteritis. Not all investigators or clinicians will agree with this designation and consider bloody diarrhea, vomiting more than 48 hours, fever higher than 101 F, dehydration, and relatively constant abdominal pain as symptoms of severe gastroenteritis. However, since these symptoms are non-specific and are more frequently associated as part of a spectrum of symptoms that occur with a specific disease that needs medical care, often quickly, these symptoms are considered as part of those that may occur with a number of specific diseases.
The majority of causes of gastroenteritis are contagious (mainly viral, bacterial, and parasitic). In some instances where the cause of the gastroenteritis is not a pathogen (for example, food allergies, toxins that are ingested), gastroenteritis is not contagious.
Most cases of gastroenteritis will get better within a few days without treatment. More severe cases may need treatment with medication. Self-care advice and information on medication is outlined below.
It is very important to replace any fluids that your body loses through diarrhoea and vomiting. Aim to drink at least 2 litres (3.5 pints) of water a day, as well as 200ml (a third of a pint) of water every time you pass diarrhoea.
If you are more vulnerable to the effects of dehydration – for example, if you are elderly or you have another pre-existing condition – then rehydration salts are recommended.
Rehydration salts are available in sachets from pharmacies. You dissolve them in water and they help to replace salt, glucose and other important minerals that your body loses via dehydration.
Some types of rehydration salts may not be suitable if you have a kidney condition. Your pharmacist or GP can give you advice on this.
Try to maintain a normal, healthy diet. Avoid foods that are high in fat and sugar because these could make your symptoms worse. You should be able to tolerate light plain foods (e.g. rice or wholemeal bread) more than spicy or rich foods.
You may find that eating up to six light meals a day is easier to tolerate than three large meals.
Medication is not usually required for the treatment for gastroenteritis unless your symptoms are particularly severe. Medications used to treat the symptoms of gastroenteritis are described below.
Antidiarrhoeal medications are used to treat the symptoms of diarrhoea. A widely used antidiarrhoeal medication for the treatment of gastroenteritis is loperamide.
Loperamide slows down the movement of your bowel contents and sometimes increases water absorption from the gut.
Loperamide is not suitable for people with colitis (inflammation of the colon).
Do not take loperamide (or any other antidiarrhoeal medication) if you have a high temperature (fever) of or above 38ºC (100.4ºF), or if you have blood and/or mucus in your stools. This is because the medication could make your symptoms worse.
Do not give antidiarrhoeal medication to children under 12 unless directly instructed to by your GP.
Anti-emetic medications are used to help prevent or reduce vomiting. They are usually only required if your vomiting is severe and places you at risk of dehydration.
A type of anti-emetic known as metoclopramide can be used for this purpose. Metoclopramide is given by injection directly into your muscles.
Metoclopramide helps to relax the muscles used during vomiting while at the same time speeding up the absorption of fluids and foods by the digestive system.
Antibiotics are not normally recommended for the treatment of gastroenteritis. This is because:
most cases of gastroenteritis are caused by viruses
even if gastroenteritis is caused by bacteria, research shows that antibiotics are often no more effective than waiting for the symptoms to pass, and they can cause unpleasant side effects
every time you use antibiotics to treat a mild condition, it is more likely that their effectiveness for treating more serious conditions is reduced
However, if your gastroenteritis is particularly severe and a specific bacterial cause has been identified, antibiotics may be recommended.
Antibiotics may also be recommended if you have a pre-existing risk factor that makes you more vulnerable to infection, such as having a weakened immune system.
Hospital treatment may be required for people with serious dehydration caused by gastroenteritis.
Admission to hospital is usually recommended when:
repeated episodes of vomiting make you unable to keep down any fluids
you have symptoms suggesting that you have severe dehydration, such as not passing any urine
Hospital treatment involves administering fluids and nutrients intravenously (directly into the vein).