Recommendations
Urgent
Viral gastroenteritis is usually self-limiting but can cause serious illness due to dehydration and electrolyte imbalance in the very young, old, and immunocompromised.[3]
Patients typically present with acute onset of watery (non-bloody) diarrhoea and/or vomiting.[3][10][11] Bloody diarrhoea, fever, and severe abdominal cramping are more likely to be non-viral in origin.
Evaluate for signs of dehydration, such as:[12][13]
Thirst
Decreased urine output
Dry mucous membranes; check tongue and mouth
Altered mental state; drowsiness.
Assess whether urgent fluid resuscitation is needed. Indicators include:[14]
Systolic blood pressure less than 100 mmHg
Heart rate more than 90 beats per minute
Cold peripheries
Respiratory rate more than 20 breaths per minute
National Early Warning Score (NEWS2) National Early Warning Score (NEWS) 2 Opens in new window of 5 or more.
Monitor patients for worsening symptoms. In the community, refer the patient to hospital if:[11]
They are severely vomiting and cannot retain fluids
They have comorbidities that increase the risk of complications
They have fever, bloody diarrhoea, or abdominal pain and tenderness (as these suggest a non-viral cause)
You suspect shock or severe dehydration
The diarrhoea has lasted for more than 10 days (and is severe).
Further investigate patients with fever, prolonged diarrhoea (lasting >14 days), severe abdominal pain, or bloody stools. These symptoms suggest a non-viral cause.
Key Recommendations
Presentation
Patients typically present with acute onset of watery (non-bloody) diarrhoea and/or vomiting.[3][10][11]
Abdominal cramps, myalgia, headache, malaise and a low-grade fever may also be present.[3][10][11]
Take a detailed clinical and exposure history. Ask about the patient’s occupation for clues to causation and to prevent outbreaks (e.g., workers in childcare facilities).
Confirming the diagnosis
Diagnose based on clinical symptoms.[10][11] Exclude non-infectious causes of diarrhoea on the basis of history and investigations.
Use blood tests to rule out coeliac disease and inflammatory bowel disease, if they are considered differentials.
Ask whether the patient is taking any medications that may have diarrhoea as a side effect.
Viral gastroenteritis cannot be differentiated from bacterial on the basis of clinical presentation. Use laboratory investigations to differentiate a viral or bacterial cause, if needed.[3][11]
History
Establish the patient’s age and comorbidities, and whether they are pregnant or immunocompromised.
Ask about occupation, travel, and food and drink eaten.
Establish the onset, duration, severity, and frequency of diarrhoea and vomiting.[13]
Investigations
Request full blood count and urea and electrolytes in patients with signs of volume depletion, and in older patients.[14] Consider bicarbonate assay, calcium, magnesium, and phosphate in patients with severe diarrhoea.
In general, testing for viral causes of gastrointestinal infections is not normally undertaken in adults unless the patient is immunocompromised.[15]
A stool sample is not needed for the diagnosis of viral diarrhoea. Stool samples for microbiological diagnosis are only needed for:[11][15]
Persistent diarrhoea (present for 14 days or longer) or malabsorption[16]
Blood, mucus, or pus in the stool, fever, or severe abdominal cramping
Systemically unwell or immunocompromised patients
A history of recent hospitalisation or for inpatients as soon as infective diarrhoea is suspected
A history of antibiotic therapy.
Also consider a stool sample when there is a history of recent foreign travel.
Causes
Norovirus, sapovirus, and rotavirus are, in order of frequency, the most commonly identified viral pathogens in gastroenteritis.[2]
Patients typically present with acute onset of watery diarrhoea (non-bloody) and/or nausea and vomiting that lasts for 2 to 5 days.[3][10][11]
The World Health Organization defines diarrhoea as at least three loose, watery stools in 24 hours.[16]
Abdominal cramps, myalgia, headache, malaise, and a low-grade fever may be present.[3][10][11]
Viral gastroenteritis cannot be differentiated from bacterial on the basis of clinical presentation. Use laboratory investigations to differentiate a viral or bacterial cause, if needed.[3][11]
Take a detailed clinical and exposure history.
Diarrhoea: ask about onset, duration, severity, and frequency.[13]
Character of the stool: watery, presence of blood or mucus.
Vomiting: ask about onset (usually acute), frequency, quantity, and character (i.e., the presence of bile or blood).
Vomiting occurs in around 80% of patients,[18] but absence does not rule out viral gastroenteritis.
Usually self-limiting.
If severe, may contribute to dehydration.
Nausea and abdominal pain may also occur.
Malaise and loss of appetite may also occur.
Fever: 40% of patients with norovirus have low-grade fever in the first 24 hours.[19]
Symptoms may last for 2 to 3 days with norovirus,[10] but may last up to 8 days with rotavirus.[20]
Consider non-infectious causes in patients with symptoms lasting longer than 14 days.[19]
Has there been recent contact with a person with gastroenteritis, or similar symptoms in household contacts?
Cases tend to cluster, and airborne transmission can occur with noroviruses and coronaviruses.
Outbreaks on cruise ships and in childcare centres are thought to be due to close contact.
For norovirus, the incubation period is usually 12 to 48 hours. Symptoms may be reported as early as 10 hours post-exposure. The infectious dose is very small: 10 to 100 virus particles.
Has the patient knowingly been exposed to any contaminated food or water sources? Noroviruses are the most common agents isolated from contaminated food or water sources.
Does the patient have reason to consider another cause for the symptoms, such as consumption of alcohol?
In addition, consider:
Has the patient recently travelled?
What is the patient’s occupation?
Ask what the patient’s recent fluid intake has been
Ask how many times the patient has passed urine in the last 24 hours
Note any:[13]
Gastroenterological disease or surgery
Endocrine disease
Radiation to the pelvis
Long-term corticosteroid use
Chemotherapy
Immunoglobulin A deficiency.
Establish the patient’s age and comorbidities, and whether they are pregnant or immunocompromised. Immunocompromised patients are likely to have more prolonged or severe illness. Older patients are at increased risk of severe dehydration.[3]
Duration of symptoms and infectivity
Norovirus, sapovirus, and rotavirus are, in order of frequency, the most commonly identified viral pathogens responsible for gastroenteritis.[2] Rotaviruses are most common in children (in countries without rotavirus vaccination programmes); noroviruses affect all ages.[3]
The onset and duration of symptoms and period of infectivity will differ depending on the causative virus.[11]
Norovirus:[10]
Consider patients are infectious while symptomatic and until symptom-free for a minimum of 48 hours or until stools have returned to their normal (pre-infection) pattern for 48 hours
Norovirus can still be detected in stools even after symptoms have resolved.
Rotavirus:[20]
Symptoms usually last 3 to 8 days
Infants and young children are most at risk
Adults may become infected but these infections are generally less severe than during childhood.
See Viral gastroenteritis in children for more information on the diagnosis and management of this condition in children.
Sapovirus:[21]
The incubation period is 1 to 4 days
Symptoms are usually self-limiting with patients recovering within a couple of days
Hospitalisation and mortality can still occur, but it has been reported that sapovirus is associated with milder symptoms than norovirus and rotavirus.
Check for dehydration. Signs and symptoms include:[12][13]
Thirst
Decreased urine output
Dry mucous membranes; check tongue and mouth
Altered mental state; drowsiness.
Indicators that the patient may need urgent fluid resuscitation include:[14]
Systolic blood pressure less than 100 mmHg
Heart rate more than 90 beats per minute
Cold peripheries
Respiratory rate more than 20 breaths per minute
National Early Warning Score (NEWS2) National Early Warning Score (NEWS) 2 Opens in new window of 5 or more.
Abdomen should be soft and only mildly tender.
If there is pain or guarding consider alternative diagnoses, such as pancreatitis, appendicitis, or inflammatory bowel disease.
A high temperature might indicate a more severe diagnosis and needs monitoring.
Viral gastroenteritis is usually self-limiting and needs no specific treatment.[3]
Most presentations of viral gastroenteritis can be managed by the patient in their own home.[22]
Symptoms may be more severe in older or immunocompromised patients.
In the community, refer to hospital if:[11]
The patient is severely vomiting and unable to retain fluids
The patient has comorbidities that increase the risk of complications
The patient has a fever, bloody diarrhoea, or severe abdominal pain and tenderness
These suggest a non-viral cause
You suspect shock or severe dehydration
Diarrhoea has lasted for more than 10 days (and is severe).
Avoid admission purely for rehydration therapy, which can be done at home.[23]
Advise the patient to seek medical help if:
Their symptoms worsen
They develop severe vomiting, severe abdominal cramps, or blood in their stools.
In general, testing for viral causes of gastrointestinal infections is not normally undertaken in adults unless the patient is immunocompromised.[15]
Full blood count
Required if considering starting intravenous fluids.[14]
Look for significant deviations from the normal values.
Anaemia may be a sign of a chronic cause of diarrhoea, such as inflammatory bowel disease.[24]
A raised haemoglobin may indicate severe dehydration.
A significantly raised or lowered WBC count can indicate an infection or inflammation.
Look at platelets as an acute-phase reactant to indicate the severity of an infection.
Urea and electrolytes
Electrolytes should be in the normal range. Both high and low values are a cause for concern.
Required if considering starting intravenous fluids.[14]
Intravenous rehydration may need to be tailored depending upon the results. Consider which fluid and the rate of administration.
Ask for serum electrolytes if you suspect serious volume depletion in which there may be hypokalaemia or renal impairment.
Consider bicarbonate assay, calcium, magnesium, and phosphate.
Patients at higher risk of complications, including older people and patients who are immunocompromised or who have comorbidities, may also need serum electrolytes.
Creatinine
Required if considering starting intravenous fluids.[14]
Normal values vary depending on age, sex, and existing comorbidities.
An abnormal result may indicate acute kidney injury.
Stool sample
Stool specimens are not needed in most patients.
Take a stool sample for microbiological diagnosis when there is:[15]
Persistent diarrhoea (present for 14 days or longer) or malabsorption[11][16]
Blood, mucus, or pus in the stool[11]
Severe abdominal pain
Suspicion of non-viral gastroenteritis
A history of recent hospitalisation or for inpatients as soon as infective diarrhoea is suspected
A history of antibiotic therapy[11]
A history of recent foreign travel.
Also consider a stool sample when there is a history of recent foreign travel.
May identify enteropathogenic bacteria or show parasitic infection. A viral stool culture is possible but rarely necessary.
Bacterial stool cultures are positive in less than 5% of presentations.[25]
A stool sample may help to exclude non-infectious causes of diarrhoea, such as adverse effects of medications, inflammatory bowel disease, coeliac disease, irritable bowel syndrome, endocrinopathy, or secretory tumours.[11]
Risk stratify patients according to level of dehydration.
Assess for volume depletion and electrolyte disturbances.
Consider the patient’s age, comorbidities, and immune status when assessing severity. Older people and immunocompromised patients are at a greater risk of mortality.[3]
Viral gastroenteritis is usually a mild, self-limiting illness, but mortality can occur.[10] Older people are susceptible to the complications of diarrhoea and account for 85% of related deaths.[25]
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