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Gastroenteritis
Usually viral and self-limiting — drinking matters more than any medicine.
Also known as: gastroenteritis · norovirus/rotavirus · stomach flu
Open in the tool — with search and all the links →This compilation is for information and replaces neither medical diagnosis nor treatment. If you have symptoms, see a doctor.
Stomach flu has nothing to do with influenza; the name simply stuck. As a rule it is a viral infection of the gut, most often from noroviruses, in small children from rotaviruses. The gut responds by pulling water into its contents and speeding the passage — unpleasant, but at heart a flushing out. So the real risk is not the germ but the loss: water, sodium, potassium. Anyone who replaces enough gets through most episodes in two to three days at home. Two practical points make the difference. First how you drink: small sips a minute apart rather than a large glass that comes straight back, and a fluid that contains salt and a little sugar alongside the water — the two are taken up together in the gut and pull the water with them. Plain water in large amounts does not replace the salt. Second hygiene: noroviruses are highly contagious, survive on surfaces and are poorly covered by alcohol hand gels — thorough handwashing with soap is the more effective measure here. You stay infectious for some days after the last episode of diarrhoea. Unusual drowsiness, a persistent refusal to drink and eat, or an age under six months are reasons in their own right to have it looked at sooner.
A large glass stretches the stomach and comes back. A teaspoon or sip every one to two minutes stays down — that is the decisive difference when vomiting.
Sodium and glucose are taken up together by the same route in the gut and pull water with them. Ready-made rehydration solutions from the pharmacy are built for this; plain sweet drinks without salt are not.
The gut lining renews faster when it has something to do. Light, salty food in small portions beats twenty-four hours of nothing.
Noroviruses have no fatty envelope for alcohol to attack. Twenty seconds of thorough washing removes them mechanically — which is why outbreaks in homes continue despite the dispensers.
The germ is still passed on in the stool when you already feel well. For kitchens, care work and childcare a wait of about forty-eight hours after the last episode therefore applies.
Remedies that shut the gut down are not indicated with fever, blood in the stool or in small children: what should leave stays in. For a day of travel in otherwise good shape they can make sense — as an exception, not a rule.
Infants, the very old, pregnant women and people with weak kidneys or diabetes lose their reserve faster. Here it pays to get help earlier rather than wait longer.
Six level teaspoons of sugar and half a teaspoon of salt in a litre of boiled water — sipped through the day.
Cook oat flakes long in water, eat lukewarm; grate an apple, let it brown, then eat.
Give a teaspoon or 5 ml of rehydration solution every five minutes, even if the child vomits — and start again after a ten-minute break.
An ordinary stomach and bowel infection is over in a few days. If it lasts, other germs come into question — giardia after travel, a bathing lake or childcare, amoebae after the tropics. The search is in the stool, and three samples on different days find more than one.
The organism survives chlorine and is passed on in the pool. The diarrhoea lasts longer than with a virus — one to two weeks — and is looked for with a test of its own.
Viral gastroenteritis lasts one to three days, with noroviruses often only twelve to sixty hours — but a person stays infectious for up to two weeks after the last loose stool. Vomiting usually stops before the diarrhoea. After vomiting, restart in small amounts: five to ten millilitres every five minutes, because larger amounts set off vomiting again. In children, wet nappies count for more than thirst.
The rehydration solution is the real medicine here: salt and sugar in the right ratio use a transport route in the gut wall that works even during inflammation — which is why it beats water or sweet drinks. Loperamide stops movement and is not the route with bloody stool or high fever. Antibiotics are of no benefit in most cases and prolong shedding of some organisms. Probiotic strains have been studied in children and shorten the diarrhoea by about a day.
That order is typical of noroviruses and often starts very suddenly, in the middle of the night. Bacterial causes tend to begin with abdominal pain and fever.
They come and go with the gut movement and ease briefly after a stool. A steady pain fixed in one spot does not fit.
Little and dark urine, a dry mouth, dizziness on standing, sunken eyes. In children add crying without tears and an unusual floppiness.
A sign that potassium is leaving with the water. This matters particularly for people taking water tablets.
Neither fits the ordinary viral course and both point to a bacterial cause or something else. That belongs examined rather than waited out.
Then it is no longer about the infection itself. Parasites, a temporary lactose intolerance after the infection or another bowel disease come into question.
The single most important hint of worms in the blood. They are raised with worms that travel through tissue — not with giardia, threadworms and amoebae, which stay in the bowel. A normal value therefore rules nothing out.
Sugar and salt are taken up in the gut through the same carrier — which is why a drinking solution works where water alone does not. That insight has saved more children’s lives worldwide than almost any other.
The amount of urine is the most honest measure of the fluid state — in children more reliable than thirst and more reliable than impression. Fewer than one wet nappy in six hours is the signal.
Anyone on standing cortisone needs more of it with vomiting and diarrhoea, not less — and if nothing stays down it belongs injected. That is the one situation in which a stomach bug becomes dangerous.
Rebuild slowly.
In acute diarrhoea certain strains shorten the duration by about half a day to a day in reviews. In children the evidence is now weaker than previously assumed.
The old bland diet of rusks and tea has been abandoned. As soon as possible normal eating resumes; replacing fluid and salt is what matters.
After diarrhoea TCM advises the bland and the cooked — the five flavours give the ordering.
AWMF 068-003 · S2k · 2024-07 — in force
Akute infektiöse Gastroenteritis im Säuglings-, Kindes- und Jugendalter
In addition:
checked 2026-09