Gastrointestinal Infections (Stomach Bugs and Diarrhoea)

Gastrointestinal infections affect the stomach and bowels. They can cause diarrhoea, vomiting, stomach cramps and feeling generally unwell. Symptoms are often caused by viral infections, contaminated food or person to person spread. Most cases improve within a few days, but some people can feel weak or dehydrated for longer.

These articles are intended as educational sources, not diagnostic nor taking place of a proper medical assessment. If you need help, please book an appointment with one of our GP’s.

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What a Gastrointestinal Infection Is

A gastrointestinal (GI) infection happens when viruses, bacteria or parasites irritate the stomach or intestines. This can develop after:

Eating or drinking contaminated food or water
Contact with someone who has a “stomach bug”
Travel, especially to higher risk regions
Poor hand hygiene or shared surfaces

The infection causes the bowel lining to become inflamed, which can lead to diarrhoea, vomiting and cramps. In most people, the body clears the infection without treatment.

Common Symptoms of Gastrointestinal Infection

You may experience:

Diarrhoea
Vomiting or feeling sick
Cramping abdominal pain
Bloating or wind
Loss of appetite
Mild fever
Tiredness or weakness
Headache or body aches

Most mild infections start to improve within 24 to 72 hours, although bowel habits can take longer to settle.

Common Reasons to Have a GI Symptoms Reviewed by a GP

Speak to a GP if you have:

Diarrhoea or vomiting lasts more than a few days
You are struggling to keep fluids down
Symptoms keep coming and going over several weeks
You have stomach pain that is not improving
You have recently travelled and feel unwell
There is mucus in the stool
You already have bowel conditions or a weakened immune system

A GP can assess whether the pattern fits with a simple stomach bug or whether further tests are needed.

Severe Symptoms – Seek Urgent Help

Seek urgent medical care if you develop:

Signs of severe dehydration, such as dizziness, passing very little urine, confusion or feeling faint
Vomiting that will not stop
Blood in the stool or black, tarry stools
Severe or worsening abdominal pain
A rigid or very tender abdomen
High fever with shaking chills
Ongoing vomiting in a frail person, an older adult or someone who is pregnant
Symptoms that rapidly worsen over a short period of time

These signs may indicate a more serious condition that needs immediate assessment.

Understanding Typical Symptom Patterns

Patterns often seen in simple viral “stomach bugs”

Sudden onset of vomiting and diarrhoea
Cramping abdominal pain that comes and goes
Low grade fever or feeling hot and cold
Several family members or contacts affected at the same time
Symptoms starting to improve within 24 to 72 hours

These patterns are typical of common viral gastroenteritis.

Patterns that may suggest food or travel related infection

Diarrhoea starting hours to days after eating a specific meal
Symptoms after travel, especially to areas with different food and water hygiene
Fever and more persistent abdominal cramps
Diarrhoea that lasts longer than expected

These patterns still need assessment, as they can overlap with non infectious causes.

Patterns that may need GP review or further testing

Diarrhoea lasting longer than 7 days
Ongoing weight loss or poor appetite
Blood or mucus in the stool
Repeated episodes over several weeks
New bowel changes in older adults
History of inflammatory bowel disease or immune problems

In these situations, a GP may consider stool tests, blood tests or referral for further investigation.

Common Organisms in Gastrointestinal Infections

These organisms are common causes of gastrointestinal infections or food poisoning. They are listed for general understanding only and do not replace clinical assessment.

Type	Organism	Notes
Viral	Norovirus	A very common cause of sudden vomiting and diarrhoea, often in clusters or outbreaks.
Viral	Rotavirus, adenovirus	Frequently seen in children, but adults can also be affected.
Bacterial	Campylobacter species	A common bacterial cause of diarrhoea, often linked with undercooked meat or poultry.
Bacterial	Salmonella species	May be associated with food or eggs that are contaminated.
Bacterial	Certain strains of E. coli	Some strains can cause diarrhoea, especially after travel or contaminated food.
Parasitic	Giardia lamblia and other parasites	More often seen after travel or exposure to untreated water, and can cause longer lasting symptoms.

When Antibiotics or Stool Tests May Be Considered

Most gastrointestinal infections are viral and do not need antibiotics. In some situations, a GP may consider stool tests or, occasionally, antibiotics. This might include:

Symptoms lasting longer than expected
High fever or blood in the stool
Recent travel to higher risk countries
Outbreaks associated with a known food source
People with reduced immunity or other serious health conditions

Antibiotics are not suitable for all causes and can sometimes make symptoms worse in certain infections. Decisions are made on an individual basis after assessment.

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How GPs Assess GI Symptoms

GPs consider:

Onset and duration of diarrhoea or vomiting
Travel history and recent food exposures
Fever, abdominal pain and weight changes
Fluid intake and urine output
Other medical conditions or medications
Whether anyone around you has similar symptoms

Examination may include checking your temperature, heart rate, blood pressure, abdomen and signs of dehydration. If needed, the GP may arrange stool tests, blood tests or refer for further review.

Managing infections at AccessGP knowledge base

How Gastrointestinal Tract Infections Are Managed

Management focuses on:

Maintaining fluid intake to prevent dehydration
Using oral rehydration solutions if advised
Taking simple pain relief if appropriate
Eating small, light meals as tolerated
Rest and avoiding heavy exertion
Practising good hand hygiene to avoid spread
Temporarily avoiding preparing food for others if you are unwell

Most people recover fully within a few days. A GP can advise on when further review is needed and how to reduce the risk of passing the infection to others.