Gastroenteritis, also referred to as "stomach flu, " is inflammation of the stomach and intestinal lining, which causes diarrhea and vomiting.
It can be caused by a virus, a bacteria or a parasite. Norovirus is the most common cause of gastroenteritis in adults. In children, rotavirus is more often involved. These viruses circulate mainly in the fall and winter. Other viruses and bacteria can spread stomach flu, especially in people travelling abroad.
Gastroenteritis is extremely contagious. You can avoid spreading and catching it through simple hygiene measures such as washing your hands.
The main symptoms of gastroenteritis are the following:
- Diarrhea: at least 3 liquid or semi-liquid stools every 24 hours or stool that is more abundant and frequent than usual
- Abdominal cramps
Other symptoms may sometimes appear:
- Mild fever
- Muscle pain
- Loss of appetite
- Change in general health (weaknesss, drowsiness, irritability, mental confusion).
Symptoms of gastroenteritis usually last 24 to 72 hours. However, they can last up to 10 days if the stomach flu began while you were travelling abroad or upon your return.
Persons with gastroenteritis are usually contagious when showing symptoms, and most particularly so when symptoms are severe. They may be contagious even a few weeks after symptoms have subsided.
If you have symptoms of gastroenteritis, it is important to stay home to heal and to avoid transmitting the illness to other people, until all symptoms have disappeared.
Gastroenteritis is generally not serious. Most people take care of themselves at home and self-heal without taking medicines. However, in some cases, you should consult a doctor or contact Info-Santé 811.
When a child should seek medical attention
When to talk with your pharmacist for your child
If your child’s bottom is irritated, talk with your pharmacist. They will advise you on the most appropriate medicated ointment.
When you should call Info-Santé 811 for your child
Call Info-Santé (option 1), if one of the following situations applies to your child:
- if your child is under the age of 2 years, regardless of the symptoms
- if your child is older than 2 years and has one of the following symptoms:
- persistent or worsening abdominal pain
- fever lasting for more than 48 hours
- frequent vomiting for 4 to 6 hours despite having followed the advice given on the page Hydrating and rehydrating when you have gastroenteritis .
- refuses to drink
- frequent and abundant diarrhea lasting for more than 7 days
- frequent diarrhea if the child is under 6 months
- moderate signs of dehydration
- your child’s general health is worrying you and you notice that their general health is getting worse
When a child should go straight to emergency
You should take your child straight to emergency if they have one of the following symptoms:
- has refused to drink for more than 4 to 6 hours
- moderate to severe signs of dehydration
- signs of mental confusion, dizziness or headache
- blood in the vomit or stool
- black stools
- vomit is bright green
- your child has a chronic disease, a weakened immune system or an immunodeficiency disorder AND has a temperature higher than 38.5 °C (101.3 °F)
When an adult should seek medical attention
When you should call Info-Santé 811
People likely to experience complications should contact Info-Santé 811. Some cases also require evaluation by a nurse. For instance, you should call Info-Santé 811 one of the following situations applies to you :
- You have diarrhea and your stools are frequent and abundant or they contain a little blood
- You are unable to drink or keep fluids down
- Your diarrhea started while you were travelling abroad or upon your return
- You are unsure whether or not to see a doctor
A nurse will give you specific advice and tell you whether or not you need to see a doctor right away.
When you should seek same-day medical attention
You should see a doctor the same day if one of the following situations applies to you:
- You have diarrhea which does not subside after 48 hours despite following instructions for rehydrating and eating when you have gastroenteritis
- You have diarrhea and fever (over 38 ºC or 100.4 ºF) for over 48 hours
- You have been vomiting for 48 hours and the situation does not improve despite following instructions for rehydrating and eating when you have gastroenteritis
- You have diarrhea that has lasted for over one week. However, if your diarrhea started during a trip abroad or upon your return, it could last more than a week
You can find a resource near you offering medical consultation on the same or next day. To learn more or to find one of those resources, see the page Finding a resource offering medical consultation on the same or next day .
When you should go straight to emergency
You should go straight to emergency if one of the following situations applies to you:
- You have a lot of blood in your stool, or your stool is black
- You have diarrhea with intense abdominal pain
- You have diarrhea, extreme thirst, have not urinated in 12 hours
- You are vomiting frequently, and it does not slow down after 4 to 6 hours
- There is stool or blood (red in colour or resembling coffee grounds) in your vomit
- Your general health is deteriorating (weakness, drowsiness, irritability, confusion)
Rehydrating yourself and eating well are the two main ways of treating gastroenteritis. To learn more, see Hydrating and rehydrating when you have gastroenteritis and Foods to eat when you have gastroenteritis.
Gastroenteritis may progress rapidly and can be dangerous, especially in infants and young children.
The main complication of gastroenteritis is dehydration. It occurs when the body eliminates too large a quantity of water and mineral salts, which are essential to the proper functioning of the body.
Watch for signs of dehydration. To avoid dehydration, follow the advice given in Hydrating and rehydrating when you have gastroenteritis.
People likely to experience complications
Some people are more at risk of experiencing complications. They include:
- Children under 2 years old
- People aged 65 years and over
- Pregnant women
- People with a chronic disease such as diabetes
If you or your child are in these categories of people and show symptoms of gastroenteritis, contact Info-Santé 811. A nurse will evaluate your condition and give you the appropriate recommendations.
Gastroenteritis is a contagious illness. An infected person can transmit the illness as long they have symptoms and up to 2 weeks after they have disappeared. He or she can be contagious even a few weeks after symptoms have subsided.
Gastroenteritis can be transmitted:
- Through consumption of contaminated water or food
- Through direct contact with a contaminated person, for example by kissing or shaking hands, if the person’s hands are contaminated with microbes from stools
- Through indirect contact with contaminated people or objects
- By eating food that has been contaminated through handling by an infected person
- By touching surfaces or objects that have been touched or handled by an infected person (example: door handles, utensils, clothes, toys)
- By touching surfaces or objects contaminated by stool or vomit
- Through breathing droplets spewed into the air, by vomit for instance
Protection and prevention
Adopt simple hygiene measures
You can protect yourself from gastroenteritis and avoid transmission by adopting simple hygiene measures:
- Wash your hands often
- Before, during and after preparing meals
- Before eating
- Before breastfeeding or feeding a child
- After using the toilet or having helped a child use the toilet
- After changing a child’s diaper
- Disinfect toilet seats and surfaces or objects that might have been contaminated by stool or vomit (such as toys or things that the child puts in their mouth).
- Put toddlers in superabsorbent diapers to prevent leakage
- Prepare and clean feeding bottles under the cleanest possible conditions
You can find additional hygiene measures on the page Steps for limiting the spread of respiratory infectious diseases.
Vaccinate your children
Rotavirus is the main virus responsible for gastroenteritis in children. Giving young children vaccination against this virus is the best way to protect them against gastroenteritis. Depending on the vaccine used, 2 or 3 doses are required. Children must receive the first dose of the vaccine before the age of 20 weeks and the last before 8 months.
For information on the vaccine against rotavirus, consult a doctor or contact Info-Santé 811.
Last update: December 18, 2023