saudigastro.com/patients/infectious-diarrhea
Category
Common
Red flags
5
This article is educational and does not replace your doctor's advice. Seek urgent care for any red-flag symptoms.
What is it?
Infectious diarrhoea, also called gastroenteritis or a stomach bug, is inflammation of the stomach and intestines caused by a virus, a bacterium or, less often, a parasite. It leads to loose or watery stools (usually three or more a day), and often nausea, vomiting, stomach cramps and sometimes fever. Viruses such as norovirus and rotavirus are the most common causes. Bacteria such as Salmonella, Campylobacter, Shigella and E. coli can cause more severe illness, sometimes with blood in the stool.
How common is it?
It is one of the most common illnesses in all age groups, and almost everyone has at least one episode every year or two. It is especially frequent in young children and in places where many people share food or living space, such as schools, nurseries, camps and large gatherings.
Why does it happen?
The germs spread through contaminated food or water, through contact with an infected person (shared utensils, unwashed hands, surfaces), and sometimes through contact with animals. Food left at warm room temperature, undercooked chicken, eggs or meat, unpasteurised milk and poorly washed salads are common sources. Hot weather and crowded events make spread easier. Recent antibiotic use or a recent hospital stay can allow a germ called Clostridioides difficile (C. difficile) to cause diarrhoea, and this needs a specific test and treatment.
Symptoms
- Loose or watery stools, three or more times a day
- Stomach cramps and pain
- Nausea and vomiting
- Fever, chills and body aches
- Loss of appetite and tiredness
- Urgent need to open the bowels
- Signs of dehydration: thirst, dry mouth, dark urine or passing little urine, dizziness
Red flags — seek urgent medical care
Signs of severe dehydration: very little or no urine for 8 hours or more, extreme thirst, confusion, fainting, sunken eyes, or in babies no tears and a sunken soft spot on the head
The body has lost too much fluid and may need drips (intravenous fluids). Go to the emergency department.
Blood or black stool, or severe constant stomach pain
May point to a more serious bacterial infection or another condition. See a doctor urgently.
Fever lasting more than about 3 days, or a very high fever
Needs assessment, and possibly a stool test.
Diarrhoea lasting more than 2 weeks, or diarrhoea after recent antibiotics or a hospital stay
Needs testing, including for C. difficile and other causes.
Persistent vomiting so that you cannot keep fluids down; or illness in a baby, an older adult, a pregnant woman, or someone with diabetes, kidney disease or a weak immune system
These groups become dehydrated faster and should be seen early.
How is it diagnosed?
In most people the doctor diagnoses gastroenteritis from your story and an examination, including checking for dehydration (pulse, blood pressure, hydration of the mouth and skin). Tests are not needed for a mild illness that is improving. A stool test is considered when there is blood in the stool, high fever, severe illness, symptoms lasting more than a week or two, recent antibiotics or hospital stay (C. difficile test), a weak immune system, or a suspected outbreak. Blood tests for kidney function and salts may be done if you are dehydrated or unwell. Tell your doctor about recent travel, what you ate, who else is ill, and any medicines you take.
What the latest science says
Current guidelines (WGO, ACG, IDSA) agree that oral rehydration is the cornerstone of treatment, that most cases need no antibiotics, and that routine stool testing is unnecessary for mild, short illnesses. Antibiotics can sometimes prolong the carrier state of some germs or cause harm, so they are kept for selected cases chosen by a doctor.
Outlook — what to expect
Excellent for almost everyone. Viral gastroenteritis usually improves within 1 to 3 days and is gone within a week. Bacterial infections may take a little longer. Appetite and bowel habit can take a week or two to return fully to normal. Serious complications are mostly due to dehydration and are largely preventable with early fluids.
Treatment
Habits & Lifestyle
Rest, fluids and good hygiene are the core of care. Hand washing also protects the rest of your family.
- Start oral rehydration solution (ORS) early and take small, frequent sips, even if you feel sick. Add more after each loose stool or vomit.
- Wash hands with soap and water for at least 20 seconds after the toilet, after changing nappies and before preparing food. Alcohol gel does not kill norovirus well.
- Stay home from work, school or nursery until 48 hours after the last loose stool or vomit. Do not prepare food for others while ill.
- Clean toilets, taps and surfaces with a bleach-based household cleaner and wash soiled clothes and bedding at a high temperature.
- Avoid hot sun and heavy exertion while recovering. During Hajj, Umrah or Ramadan heat, dehydration develops quickly, so seek medical help earlier.
Diet
Fluids come first; food can follow as soon as you feel able. You do not need to starve the bowel.
- Oral rehydration solution is the best drink. Ready-made sachets from the pharmacy mixed exactly as the label says are safe. Do not add extra sugar or salt to them.
- Soups, clear broths, and water are helpful. Avoid very sugary drinks such as soft drinks, packaged juices and energy drinks on their own, as they can make diarrhoea worse.
- Eat small, plain meals as soon as you can: rice, bread, bananas, potatoes, yoghurt. Return to normal food within a day or two.
- Breastfed babies should continue to breastfeed. Children should keep eating normally as soon as they are able.
- Avoid greasy, spicy food, alcohol and too much caffeine until recovered. Some people temporarily cannot digest milk sugar (lactose); if milk worsens things, avoid it for a week or so.
Medications
Most people need no medicine other than fluids. Always check with a doctor or pharmacist before using anti-diarrhoea medicines or antibiotics.
- Antibiotics are NOT needed for most infectious diarrhoea, and do not help viral illness. Take them only if a doctor prescribes them after assessing you. Never use leftover antibiotics.
- Loperamide (an anti-motility medicine) can ease symptoms in healthy adults with watery diarrhoea only. Do NOT use it in children, or when there is blood in the stool, fever or severe abdominal pain, unless a doctor advises it.
- Paracetamol can be used for fever or aches as the label and your doctor advise. Avoid anti-inflammatory painkillers (ibuprofen, diclofenac) when dehydrated because they can harm the kidneys.
- Anti-sickness medicines may be given by a doctor if vomiting stops you drinking.
- If you take water tablets (diuretics), blood pressure or diabetes medicines, ask your doctor whether to pause them while you are dehydrated. Do not stop any medicine without advice.
Procedures & Surgery
Procedures are not usually needed. Hospital care is for people who are dehydrated or very unwell.
- Intravenous (drip) fluids are given in hospital if you cannot drink enough or are severely dehydrated.
- Stool tests or, rarely, a colonoscopy (camera test of the large bowel) are used only if diarrhoea persists or the cause is unclear.
Living with the condition
- Wash hands well and often, especially before eating and after the toilet. This is the single most effective prevention.
- Keep raw and cooked food separate, cook chicken, meat and eggs thoroughly, and refrigerate leftovers quickly. Do not leave rice, meat or sauces out in the heat for hours.
- Use safe, sealed bottled or properly treated water at gatherings and when water quality is uncertain. Wash fruit and salad vegetables well.
- Rotavirus vaccination for babies is part of routine childhood immunisation and greatly reduces severe diarrhoea in infants. Ask your child’s clinic.
In the Saudi context
High summer temperatures, large family meals, buffets, outdoor events and mass gatherings such as Hajj, Umrah and Ramadan iftars all increase the chance of food-borne illness and make dehydration develop faster. Keep ORS at home and in your travel bag, keep cooked food chilled, and avoid food that has been sitting out in the heat.
Questions to ask your doctor
Save this list or print it before your appointment — doctors appreciate prepared patients.
- Do I need a stool test or antibiotics?
- How much ORS should I drink, and for how long?
- Is it safe for me to take loperamide?
- Should I pause any of my regular medicines while I am unwell?
- When can my child return to school, and when can I return to work?
Trusted resources
Was this guide helpful?
Status: Approved for publication by SGA; individual clinician review is ongoing · Published 24/04/2026
For general education only; it does not replace your doctor’s advice. Individual clinician review of this guide is ongoing. SGA clinician? Review this guide