Gastric flu - Symptoms of gastroenteritis
NHS Choices Medical Reference
In cases of viral gastroenteritis, symptoms usually begin within 24-48 hours after becoming infected (this time period is known as the incubation period).
The incubation period for bacterial gastroenteritis can range from 12 hours to five days, depending on the bacterium responsible.
The most common symptom of gastroenteritis is repeated episodes of diarrhoea. Usually, loose and watery stools are passed three or more times within 24 hours. The stools may contain traces of blood and mucus.
Other symptoms of gastroenteritis include:
- stomach cramps
- moderately high temperature (fever) of 38-39ºC (100.4-102.2ºF)
Be alert for symptoms suggesting that you or someone in your care are becoming dehydrated (where the water content of the body is particularly low).
Dehydration can cause serious and potentially fatal complications. Elderly people are particularly vulnerable to the effects of dehydration.
Symptoms of dehydration include:
- apathy (a lack of emotion or enthusiasm)
- muscle cramps
- dry mouth
- pinched face
- sunken eyes
- passing little or no urine
- rapid heartbeat
See treating dehydration for advice on how to counter the effects of dehydration.
When to seek medical advice
Most cases of gastroenteritis do not need medical treatment as the symptoms will pass within a few days - typically two to three days for viral gastroenteritis and four to seven days for bacterial gastroenteritis.
There may be circumstances where medical treatment is required. Contact your GP if you have any of the following:
- vomiting that lasts more than two days
- you cannot keep liquids down for more than a day
- diarrhoea that lasts more than three days
- blood in your vomit
- blood in your stools
- seizures (fits)
- changes in mental state, such as confusion
- double vision
- slurred speech
- signs of dehydration, such as a dry mouth, sunken eyes and being unable to pass urine
- your symptoms do not begin to improve after three days
- you suspect that you caught gastroenteritis while travelling in the developing world; particularly if you were visiting a part of the world with a poor standard of water hygiene
Parts of the world known to have poor levels of water hygiene include:
- sub-Saharan Africa (all the countries south of the Sahara Desert)
- countries in South Asia, such as India, Bangladesh and Pakistan
- Central and South America
Also contact your GP if you have pre-existing risk factors that make you vulnerable to developing a serious complication from infections, such as:
Blood: Blood supplies oxygen to the body and removes carbon dioxide. It is pumped around the body by the heart.
Dehydration: Dehydration is an excessive loss of fluids and minerals from the body.
Diarrhoea: Diarrhoea is the passing of frequent watery stools when you go to the toilet.
Faeces: Stool (also known as faeces) is the solid waste matter that is passed from the body as a bowel movement.
Fever: A high temperature, also known as a fever, is when someone's body temperature goes above the normal 37°C (98.6°F).
Loss of appetite: Loss of appetite is when you do not feel hungry or want to eat.
Pain: Pain is an unpleasant physical or emotional feeling that your body produces as a warning sign that it has been damaged.
Vomiting: Vomiting is when you bring up the contents of your stomach through your mouth.