Stomach Flu & Food Poisoning (Gastroenteritis) - Symptoms & Causes

What is gastroenteritis?

Gastroenteritis is an infection that leads to the inflammation of the stomach or the intestine. The condition can happen to anyone but may be more common in children and the elderly due to their weaker immune systems.

Depending on the cause, it may also be known as stomach (gastric) flu or food poisoning.

What are the symptoms of stomach flu or food poisoning?

In general, the symptoms of stomach flu and food poisoning are similar and may include:

  • Fever
  • Nausea
  • Vomiting
  • Headache
  • Watery diarrhoea
  • Stomach pain and cramps

In rare cases, stomach flu can leave you severely dehydrated. Watch out for:

  • Dizziness
  • Dry mouth
  • Sunken eyes
  • Intense thirst
  • Blurred vision
  • Feeling foggy or unable to focus
  • Reduced urine output

When to seek medical attention?

You should visit the Urgent Care Centre (UCC) if:

  • You are pregnant.
  • You have a fever of more than 38°C.
  • Your vomiting lasts more than a day.
  • Your diarrhoea lasts more than 2 days.
  • You experience severe abdominal pain.
  • You notice blood in your vomit or stools.
  • You have a chronic illness, such as diabetes, kidney disease or heart problems.

Stomach flu in children may result in serious illness. You should bring your child to a doctor if your child displays any of the following symptoms:

  • Green vomit
  • Blood in vomit or stools
  • Fever of more than 38°C
  • Diarrhoea beyond 2 weeks
  • Drowsiness or increased lethargy
  • Severe or prolonged episodes of abdominal pain
  • A sunken fontanelle (the soft spot on top of the skull)
  • Continuous vomiting and inability to keep down any fluids
  • Large amounts of watery diarrhoea more than 8 – 10 times a day
  • Signs of dehydration such as poor urine output, dry lips or tongue, sunken eyes

What causes gastroenteritis?

In general, gastroenteritis may be caused by viruses, bacteria or parasites:

Stomach flu

Stomach flu is caused by viruses, such as the rotavirus or norovirus. Norovirus is the most common cause of acute gastroenteritis. Other viruses include the astrovirus and adenovirus. Symptoms typically appear within 1 – 3 days of exposure to the virus.

Viral gastroenteritis may be transmitted through:

  • Physical contact with an infected individual
  • Contact with contaminated objects, such as utensils and toys

Food poisoning

Food poisoning is caused by bacteria, viruses or parasites in contaminated food. Symptoms typically appear within 1 hour – 7 days of consumption.

Common sources of food poisoning include:

  • Unwashed fruit or vegetables
  • Raw eggs, meat, fish or shellfish
  • Leftover rice that was not reheated adequately
  • Unpasteurised soft cheese or milk

Gastroenteritis can cause severe, even life-threatening, complications in vulnerable people, including:

  • Young children
  • Pregnant women
  • Those taking medications to suppress their immune system
  • Those with poor immune systems
  • The elderly

Children and infants are at particular risk of severe symptoms from gastroenteritis because they become dehydrated much faster than adults.

How to prevent gastroenteritis?

Gastroenteritis is not fully preventable, though vaccinations are available for some of the viruses that cause it. For example, the rotavirus vaccine can be given to infants at 3 – 8 months to prevent severe cases of rotavirus gastroenteritis.

Besides vaccination, you can prevent gastroenteritis by:

  • Avoiding raw or undercooked food
  • Avoiding physical contact with someone who has gastroenteritis
  • Maintaining good hygiene practices such as regular hand-washing
  • Sanitising surfaces, such as your kitchen counter or work desk, regularly
  • Washing your hands before cooking or handling food
  • Keeping raw foods separate from ready-to-eat foods
  • Refrigerating and freezing perishable food promptly
  • Not sharing cups or utensils

Note: It is possible to contract gastroenteritis more than once as there are many strains of viruses that cause gastroenteritis.

This page has been reviewed by our medical content reviewers.

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