Gastroenteritis (Food Poisoning)

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What is

Symptoms

How to prevent

Causes and Risk Factors

Diagnosis

Treatment

FAQs

What is - Gastroenteritis (Food Poisoning)

What is gastroenteritis?

Gastroenteritis, often called food poisoning, is a common illness that causes diarrhoea or vomiting. It happens when bacteria, viruses or parasites in contaminated food or water cause your stomach or intestines to be inflamed.

How do you get gastroenteritis?

Food that is undercooked, not stored properly or left out too long can let harmful germs grow. Drinking unclean water or poor food handling can also cause infection.

What are the types of gastroenteritis?

Viral: The most common type (e.g., Norovirus, rotavirus)
Bacterial: E.g., Salmonella, E. Coli, Campylobacter
Parasites: More common in places with poor sanitation (e.g., Giardia, Cryptosporidium)
Non-infectious: Caused by food intolerances (e.g., lactose intolerance, gluten sensitivity, food allergies), medications (e.g., antibiotics, chemotherapy) or inflammation (e.g., inflammatory bowel diseases such as ulcerative colitis or Crohn’s disease)

Most causes of infective diarrhoea are self-limiting and usually resolve by three weeks. Chronic diarrhoea that persists for more than three weeks should prompt further medical consultation.

Symptoms of Gastroenteritis (Food Poisoning)

What are the symptoms of gastroenteritis?

Symptoms include:

Diarrhoea, increased stool frequency or loose stools
Blood in stool
Vomiting
Abdominal pain or stomach cramps
Fever

When should you see a doctor?

Medical advice should be sought under the following circumstances:

If diarrhoea persists for more than one week despite adequate self-medication with hydration and anti-diarrhoeal agents.
If you have just returned from an area endemic with cholera (especially if your diarrhoea is profuse and watery).
If you are unable to keep body hydrated due to severe vomiting. This means your doctor may need to give you intravenous fluids for a few days. The very young and old persons are particularly at risk.
If your stool shows blood and pus.
If you have high running fever.

Gastroenteritis (Food Poisoning) - How to prevent

How can gastroenteritis be prevented?

Practising good hygiene and food safety measures can help reduce the risk of gastroenteritis.

Wash hands thoroughly with soap and water before eating, after using the toilet and after handling raw food
Cook meat, poultry, seafood and eggs to the recommended temperatures to kill harmful bacteria
Store perishable foods in the refrigerator and avoid leaving cooked food at room temperature for extended periods
Wash fruits and vegetables thoroughly before consumption
Use separate chopping boards for raw and cooked food
Drink clean, filtered or bottled water in areas where water safety is uncertain

Gastroenteritis (Food Poisoning) - Causes and Risk Factors

What are the risk factors for gastroenteritis?

Certain factors can increase the risk of developing gastroenteritis.

Consumption of contaminated food or water: Poorly cooked, raw or unpasteurised food, as well as untreated water, can harbour bacteria, viruses or parasites
Poor food handling and hygiene: Cross-contamination, inadequate handwashing and improper food storage can increase the risk of infection
Weakened immune system: People with chronic illnesses, those undergoing chemotherapy or individuals with conditions such as diabetes are more vulnerable to severe infections
Travelling to high-risk areas: Visiting regions with poor sanitation or different food preparation standards increases exposure to harmful pathogens
Age-related vulnerability: Infants, young children, older adults and pregnant women are more susceptible to complications from gastroenteritis
Exposure to infected individuals: Close contact with someone who has gastroenteritis, especially in households, schools or care facilities, increases the likelihood of transmission

Diagnosis of Gastroenteritis (Food Poisoning)

How is gastroenteritis diagnosed?

Gastroenteritis is diagnosed based on symptoms, medical history and a physical examination.

In cases that are severe or prolonged, additional investigations are required. These include stool tests to detect bacteria, viruses or parasites, blood tests to check for infection or dehydration and imaging or endoscopy in selected patients.

Treatment for Gastroenteritis (Food Poisoning)

How is gastroenteritis treated?

Diarrhoea can usually be treated effectively by self-medication.

Hydration and fluid replacement

The mainstay of therapy is adequate hydration. Illness is usually self-limiting and does not require any specific medical therapy. The overwhelming majority of adults have mild diarrhoea that will not lead to dehydration provided adequate fluids are taken.

Hydration can be achieved by drinking boiled barley or rice water with a sprinkle of salt. This formulation helps to increase water absorption across the gut wall. An easier way is to consume commercially available oral rehydration salts in tablets or sachets form (Rehidrat, Dioralyte). These tablets can be drunk after reconstitution in boiled water (Please read the manufacturer's instructions for methods of dilution).

Dietary considerations

Most people will find it more comfortable to rest the bowel for a few days by avoiding high-fibre, high-fat foods. Frequent feedings of fruit drinks, tea, de-fizzed carbonated beverages and soft easily digested foods (eg. soups, crackers) are encouraged.

Antibiotics

Routine use of antibiotics is not recommended as illness is self-limiting and the majority of cases are causes by viruses and not bacteria. Antibiotics are indicated for those persons with high fever and prolonged diarrhoea.

Anti-diarrhoeal medications

Anti-diarrhoeal agents (such Lomotil) work by decreasing bowel contraction and may be used to decrease the frequency of diarrhoea, liquidity of stool and abdominal cramps. It should not be used if there is a high fever and blood is present in the stool indicating severe large bowel inflammation. This drug should also be discontinued and medical advice should be sought if diarrhoea worsens after a few days of therapy.

Lactose avoidance

Avoidance of milk and milk products is recommended for the first few weeks to avoid worsening of the diarrhoea from lactase deficiency. Gastroenteritis can reduce the concentration of the enzyme lactase and thus the ability of the small bowel to digest lactose present in milk.

FAQs on Gastroenteritis (Food Poisoning)

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Illness is usually self-limiting and lasts for 3 to 4 days. If diarrhoea is prolonged for more than one week, you are advised to visit your doctor for assessment and to obtain a course of antibiotics.

Most people recover from an attack of gastroenteritis without any complications. In a minority of patients who fail to keep up with the loss of water in their stool, their body may become too dry and this can result in kidney failure.

If the symptoms are severe or prolonged, your doctor may order stool specimens for culture, blood tests to check for white counts and degree of dehydration.

Prevention lies in the adherence to standard food-handling techniques, with particular attention paid to avoiding the multiplication of the organism within food (i.e. proper heating and the prompt refrigeration after cooking of food items). This basic principle of food handling applies just as much to you as it does to your favourite hawker stalls.

High-risk areas for traveller's diarrhoea include developing regions where endemic diarrhoea rates are highest. This includes Latin America, Africa, the Middle East and parts of Asia. Developed nations such as the United States, Europe and Australia pose the lowest risk.

Travellers from low-risk, industrialised countries face a higher risk when visiting high-risk areas. The illness appears to be associated with more frequent reliance on public rather than private eating establishments and alterations in diet.

Illness is usually self-limiting and lasts for three to four days if left untreated. Mortality from the illness is almost non-existent but morbidity can be considerable, confining travellers to bed in up to 30% of cases or altering 40% of itineraries.

Escherichae coli (E. coli) is a common cause of traveller's diarrhoea, accounting for up to 70% of cases. Acquisition of these pathogenic agents is through ingestion of contaminated food or water.

What can I do to prevent getting traveller's diarrhoea?

Raw vegetables, raw meat or seafood and other moist foods maintained at room temperature are high-risk items. Tap water and ice are also considered to be unsafe. In general, food should be chosen if it is served piping hot. The risk for the development of traveller’s diarrhoea increases when eating at restaurants, particularly when eating food purchased from street vendors. Safe food items include boiled or bottled water and beverages, canned products and fruits that can be peeled.

Studies have shown that prophylactic antibiotics are effective in reducing the frequency of traveller’s diarrhoea, but this is generally not recommended due to side effects inherent with antibiotics consumption, especially with prolonged use.

Can I self-medicate for traveller’s diarrhoea?

Oral fluid is the mainstay of therapy.

If symptoms are moderately severe (stool frequency of up to 5x per day), anti-diarrhoeal agents such as loperamide (Lomotil) at 4mg three times per day are recommended.Medical opinion and antibiotics are recommended if the frequency of diarrhoea is more than 6 times per day especially if there is associated fever or blood in the stools.

Cholera

Cholera is caused by the bacterium Vibrio cholerae and is endemic in southern Asia, Africa and Latin America, where overcrowding and poor water and waste sanitation contribute to its spread. Faecally contaminated water and seafood are the major vehicles of transmission for cholera.

Illness is caused by the bacterial toxin that induces the small bowel mucosa from an 'active absorber' of water to a 'secretor' of water. Illness varies from mild gastroenteritis to severe profuse watery diarrhoea.

Faecal material has been described as of 'rice water' consistency. Up to one litre of water per hour can be lost in the diarrhoea. Diagnosis is made by isolation of the organism from the stool. The main line of treatment is rehydration through oral or intravenous routes. Antibiotic is generally given as it shortens the duration of illness.

Antibiotic associated diarrhoea

Diarrhoea may occur during or after a course of antibiotics; there is usually no obvious pathogen. Symptoms usually resolve after the completion of antibiotics. The course is benign and does not require any therapy.

However, the severe end of antibiotic-associated diarrhoea is a condition called pseudomembranous colitis. This is so called because there is inflammation of the large bowel with a layer of mucus overlying the surface. There is suppression of the usual 'resident' bacteria which keeps the large bowel in healthy condition by the antibiotics with subsequent overgrowth of 'harmful' bacteria (Clostridium difficle).

This bacteria secretes a toxin which causes inflammation to the large bowel. A symptom indicating this condition is diarrhoea associated with the passage of blood and mucus. If you have an onset of diarrhoea after a recent course of antibiotics and the stool is bloody, you should visit your doctor to get the appropriate therapy.