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# Acute (viral) gastroenteritis

Acute gastroenteritis is inflammation of the [stomach](https://durgical.com/en/anatomy/stomach/) and intestines, usually viral, with sudden diarrhoea and vomiting; dehydration is the main danger.

Updated 2026-10-30

## Structures involved

Tap one to see what it is and open it in 3D.

- [Stomach](https://durgical.com/en/anatomy/stomach/)
- [Jejunum](https://durgical.com/en/anatomy/jejunum/)
- [Ileum](https://durgical.com/en/anatomy/ileum/)
- [Duodenum](https://durgical.com/en/anatomy/duodenum/)
- [Cecum](https://durgical.com/en/anatomy/cecum/)
- [Ascending colon](https://durgical.com/en/anatomy/ascending-colon/)
- [Mesenteric lymph nodes](https://durgical.com/en/anatomy/superior-mesenteric-nodes/)

## In biochemistry

- [Zinc](https://durgical.com/en/biochemistry/topics/zinc/)

## Microorganisms that cause it

- [Vibrio vulnificus and Vibrio parahaemolyticus](https://durgical.com/en/microbiology/vibrio-vulnificus-and-vibrio-parahaemolyticus/)
- [Escherichia coli](https://durgical.com/en/microbiology/escherichia-coli/)
- [Non-typhoidal Salmonella](https://durgical.com/en/microbiology/non-typhoidal-salmonella/)
- [Yersinia](https://durgical.com/en/microbiology/yersinia/)
- [Campylobacter jejuni](https://durgical.com/en/microbiology/campylobacter-jejuni/)
- [Clostridium perfringens](https://durgical.com/en/microbiology/clostridium-perfringens/)
- [Bacillus cereus](https://durgical.com/en/microbiology/bacillus-cereus/)
- [Giardia duodenalis](https://durgical.com/en/microbiology/giardia-duodenalis/)
- [Cryptosporidium spp.](https://durgical.com/en/microbiology/cryptosporidium-spp/)
- [Cyclospora cayetanensis and Cystoisospora belli](https://durgical.com/en/microbiology/cyclospora-cayetanensis-and-cystoisospora-belli/)
- [Adenovirus](https://durgical.com/en/microbiology/adenovirus/)
- [Rotavirus](https://durgical.com/en/microbiology/rotavirus/)
- [Norovirus](https://durgical.com/en/microbiology/norovirus/)

## In the clinical exam

- [Dehydration and fluid overload](https://durgical.com/en/clinical-exam/dehydration-and-fluid-overload/)

## In physiology

- [Carbohydrate digestion and absorption](https://durgical.com/en/physiology/carbohydrate-digestion-and-absorption/)
- [Water and electrolyte absorption and how diarrhea happens](https://durgical.com/en/physiology/water-and-electrolyte-absorption-and-how-diarrhea-happens/)
- [Vomiting and its control](https://durgical.com/en/physiology/vomiting-and-its-control/)
- [Potassium balance](https://durgical.com/en/physiology/potassium-balance/)
- [Metabolic acidosis, the anion gap and compensation](https://durgical.com/en/physiology/metabolic-acidosis-the-anion-gap-and-compensation/)
- [Dehydration and fluid overload](https://durgical.com/en/physiology/dehydration-and-fluid-overload/)

## Why it happens

- [Health effects of climate change](https://durgical.com/en/general-pathology/health-effects-of-climate-change/)
- [Severe acute malnutrition: marasmus and kwashiorkor](https://durgical.com/en/general-pathology/severe-acute-malnutrition-marasmus-and-kwashiorkor/)
- [Small intestine: villi, crypts, enterocytes, Paneth cells; duodenum vs jejunum vs ileum](https://durgical.com/en/histology/small-intestine-villi-crypts-enterocytes-paneth-cells-duodenum-vs-jejunum-vs-ile/)

## What it is

Acute inflammation of the stomach and intestines, most often caused by viruses, with sudden diarrhoea, often vomiting, that usually resolves within a few days; dehydration is the main danger.

## Who gets it

Very common at all ages and still an important cause of child illness in Latin America. Norovirus leads outbreaks at all ages; rotavirus, once the main cause of severe child diarrhoea, has fallen where its vaccine is used, as in Colombia. In Bucaramanga, Colombia (2013–2014), norovirus GII explained an estimated 14% and rotavirus 9.3% of moderate to severe cases under age 5.

## Causes

- Norovirus (outbreaks at all ages: schools, cruise ships, care homes)
- Rotavirus (infants and young children)
- Enteric adenovirus, astrovirus and sapovirus
- Spread by the faecal-oral route: hands, contaminated food or water, surfaces; vomit aerosols with norovirus

## Risk factors

- Young children and older adults (higher risk of dehydration)
- Day care, schools, care homes, ships
- Poor hand hygiene, unsafe water and sanitation
- Lack of rotavirus vaccination
- Immunosuppression

## Pathophysiology

Viruses infect and damage the cells on the tips of the small bowel villi, reducing absorption and digestive enzymes and causing osmotic diarrhoea. Rotavirus also produces a toxin (NSP4) that drives secretion. Loss of water and salts by stool and vomiting leads to dehydration, electrolyte disorders and acidosis.

## Classification

- Dehydration by WHO categories: no dehydration, some dehydration, severe dehydration
- Watery diarrhoea versus bloody diarrhoea (dysentery, suggests a bacterial or parasitic cause)

## Symptoms and signs

- Sudden watery diarrhoea without blood
- Nausea and vomiting, often first (marked in norovirus)
- Crampy abdominal pain
- Low-grade fever, muscle aches
- Signs of dehydration: thirst, dry mouth, few tears, less urine

## Red flags

- Severe dehydration: lethargy, sunken eyes, unable to drink, very slow skin pinch
- Bloody diarrhoea
- Persistent vomiting preventing oral rehydration
- Severe or localised abdominal pain, distension (surgical cause)
- Infants, malnourished or immunosuppressed patients; symptoms lasting more than a week

## Diagnosis

**Clinical**
Mainly clinical. Dehydration is graded by general condition, eyes, thirst and [skin](https://durgical.com/en/anatomy/skin/) pinch (WHO assessment); weight loss is the most accurate measure when a recent weight is known.

**Tests**
Usually not needed. Electrolytes, glucose and renal function in moderate to severe dehydration. Stool tests (viral antigen or molecular panels) in outbreaks, bloody diarrhoea, hospital patients or the immunosuppressed.

**Imaging**
Not routinely used; abdominal ultrasound or other imaging only if a surgical cause is suspected.

## Differential diagnosis

- Bacterial or parasitic gastroenteritis (Salmonella, Shigella, Campylobacter, Giardia, amoebiasis)
- Acute appendicitis
- Intussusception (infants)
- Diabetic ketoacidosis
- Urinary tract infection or other infections with vomiting
- Food poisoning (preformed toxins)

## Goal of treatment

Prevent and correct dehydration, keep nutrition going and avoid spreading the infection while the illness runs its course.

## Treatment

**Conservative**
Oral rehydration with reduced-osmolarity oral rehydration salts (WHO ORS) for no or some dehydration, given in small, frequent sips.

**Lifestyle**
Continued breastfeeding and normal age-appropriate feeding once rehydrated.

**Medical**
Zinc supplementation for children with diarrhoea, as recommended by WHO.

**Acute**
Intravenous fluids for severe dehydration, shock or failure of oral rehydration.

**Medical**
An antiemetic (5-HT3 antagonist) in selected children with vomiting to allow oral rehydration.

**Medical**
Antibiotics are not used for viral gastroenteritis; antimotility agents are avoided in young children and in bloody diarrhoea.

## Drugs for this condition

- [Ondansetron](https://durgical.com/en/pharmacology/ondansetron/)
- [Loperamide](https://durgical.com/en/pharmacology/loperamide/)
- [Oral rehydration salts](https://durgical.com/en/pharmacology/oral-rehydration-salts/)
- [Rotavirus vaccine](https://durgical.com/en/pharmacology/rotavirus-vaccine/)

## Complications

- Dehydration and hypovolaemic shock
- Electrolyte disorders (sodium, potassium) and metabolic acidosis
- Acute [kidney](https://durgical.com/en/anatomy/kidney/) injury
- Temporary lactose intolerance
- Post-infectious irritable bowel syndrome

## Prognosis

Usually self-limited within a few days with full recovery. Deaths are mostly from dehydration in young children, older adults and malnourished people, and are largely preventable with oral rehydration.

## Prevention

- Handwashing with soap and water (alcohol gel is less effective against norovirus)
- Rotavirus vaccination in infancy
- Safe water, sanitation and food hygiene
- Cleaning surfaces with chlorine-based products and staying off work or school until symptoms end

## Test yourself

Think of the answer, then tap the question to see it.

## Which virus causes most outbreaks of gastroenteritis in all age groups?

Norovirus.

## Which virus was the main cause of severe childhood diarrhoea before vaccination?

Rotavirus; routine infant vaccination has reduced severe cases and hospital admissions.

## What is the main treatment of viral gastroenteritis with mild to moderate dehydration?

Oral rehydration with reduced-osmolarity oral rehydration salts (WHO ORS), plus continued feeding.

## Which clinical signs suggest severe dehydration in a child?

Lethargy or unconsciousness, sunken eyes, inability to drink and a skin pinch that goes back very slowly.

## Why are antibiotics not used in viral gastroenteritis?

They do not act on viruses, do not shorten the illness and can cause side effects and resistance.

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## Related conditions

- [Hypovolaemic shock](https://durgical.com/en/conditions/hypovolaemic-shock/)
- [Acute appendicitis](https://durgical.com/en/conditions/acute-appendicitis/)
- [Irritable bowel syndrome](https://durgical.com/en/conditions/irritable-bowel-syndrome/)
- [Intussusception (children)](https://durgical.com/en/conditions/intussusception/)
- [Urinary tract infection (acute cystitis)](https://durgical.com/en/conditions/urinary-tract-infection/)
- [Amoebic liver abscess](https://durgical.com/en/conditions/amoebic-liver-abscess/)
- [Infantile hypertrophic pyloric stenosis](https://durgical.com/en/conditions/infantile-hypertrophic-pyloric-stenosis/)

Educational information, not medical advice. For any symptom, see a health professional.

Sources: [Viral Gastroenteritis](https://www.ncbi.nlm.nih.gov/books/NBK518995/) (StatPearls (NCBI Bookshelf), 2025); [Etiology of acute gastroenteritis among children less than 5 years of age in Bucaramanga, Colombia: A case-control study](https://europepmc.org/article/PMC/PMC7357789) (PLoS neglected tropical diseases, 2020) · adapted, [CC BY 4.0](https://creativecommons.org/licenses/by/4.0/).

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/conditions/acute-gastroenteritis/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/conditions/acute-gastroenteritis/