What is gastroenteritis?
Gastroenteritis is inflammation of the lining of the stomach and intestines, most often caused by an infection. It is what most people mean by a stomach bug or tummy bug, and sometimes it is loosely called stomach flu, although it is not related to influenza. It leads to the classic combination of diarrhoea and vomiting, often with stomach cramps and feeling generally unwell.
It is extremely common and usually short-lived, clearing up on its own within a few days as the body fights off the infection. Gastroenteritis spreads easily from person to person and through contaminated food or water, which is why outbreaks can occur in households, schools and other settings. While unpleasant, it is usually not serious in otherwise healthy people. The main concern, particularly in young children and older adults, is dehydration from the fluid lost through diarrhoea and vomiting.
Symptoms
The symptoms of gastroenteritis usually come on fairly suddenly and centre on the digestive system. They can range from mild to quite debilitating for a few days. Common symptoms include:
- •Diarrhoea, which may be watery
- •Feeling sick (nausea) and being sick (vomiting)
- •Stomach cramps or tummy pain
- •A mild fever, headache and aching limbs in some cases
- •Loss of appetite
- •Feeling generally unwell and tired
Common causes
Gastroenteritis is usually caused by an infection, which can be viral, bacterial or, less commonly, parasitic. It spreads through contact with an infected person, or through contaminated food or water. Common causes include:
- •Viruses, such as norovirus (a very common cause) and rotavirus (especially in children)
- •Bacteria, often from contaminated food (a form of food poisoning)
- •Contact with someone who has the infection
- •Touching contaminated surfaces then the mouth
- •Occasionally, parasites from contaminated water
Treatment and staying hydrated
Most cases of gastroenteritis clear up on their own without specific treatment, and the most important thing is to stay hydrated, since diarrhoea and vomiting cause fluid loss. Drink plenty of fluids in small, frequent sips, which are easier to keep down than large amounts. Oral rehydration sachets from a pharmacy help replace lost salts and fluids and are especially useful for those at higher risk of dehydration.
Rest, and eat when you feel able, starting with small, plain foods — there is no need to starve yourself, though you may not feel like eating much at first. Antibiotics are not usually needed, as most gastroenteritis is viral, and are only used in specific bacterial or parasitic cases identified by a doctor. Anti-sickness or anti-diarrhoeal medicines are not always suitable, particularly for children, so a pharmacist can advise. Watch for signs of dehydration and seek help if they develop, especially in young children and older adults.
Preventing the spread
Gastroenteritis, particularly norovirus, is highly contagious and spreads easily, so good hygiene is the main way to reduce its spread within households and communities. Washing hands thoroughly with soap and water — especially after using the toilet, before preparing or eating food, and after caring for someone who is unwell — is the single most effective measure. Alcohol hand gels are less effective against some causes like norovirus, so soap and water is best.
If you have gastroenteritis, staying off work or school until at least 48 hours after your symptoms have stopped helps avoid passing it on, as you can remain infectious for a short time after feeling better. Cleaning contaminated surfaces, not sharing towels, and washing soiled laundry separately at a high temperature also help. Careful food and water hygiene — storing, preparing and cooking food properly — reduces the risk of the food-related causes.
Because gastroenteritis spreads so readily, these simple steps make a real difference during outbreaks. For young children, a rotavirus vaccine is offered in many places and protects against one of the common causes. Overall, good hand hygiene remains the cornerstone of prevention, both for avoiding infection and for stopping it spreading to others once someone in the household is affected.
Who is most at risk from gastroenteritis
While gastroenteritis is usually mild and self-limiting in otherwise healthy people, some groups are more vulnerable to its effects, chiefly because of the risk of dehydration. Babies and young children can become dehydrated quickly, as can older adults, so both groups warrant closer watching and a lower threshold for seeking advice. People with weakened immune systems, or with certain long-term conditions, may also be more affected and take longer to recover.
For these higher-risk groups, the priority remains hydration, but with extra vigilance. In young children, signs of dehydration include fewer wet nappies, dryness, drowsiness, and sunken features; in older adults, confusion, dizziness and passing little urine are warning signs. Oral rehydration solutions are particularly valuable for these groups, and medical advice should be sought earlier rather than later if there is any concern.
The reassuring point is that even in higher-risk groups, most gastroenteritis still resolves within a few days with good hydration and care. Knowing who needs extra watching, and what dehydration looks like, allows carers and family members to act promptly when needed while managing most cases confidently at home.