Viral Gastroenteritis (Stomach Flu)

What is viral gastroenteritis?

Gastroenteritis (say: GAS-tro-enter-EYE-tis) is the inflammation of the stomach and small and large intestines. Viral gastroenteritis means the inflammation is caused by infection with a virus. It often causes vomiting (throwing up) or diarrhea.

Viral gastroenteritis is often called "stomach flu," but it is not caused by flu (influenza) viruses. Viral gastroenteritis can be caused by many different viruses, including Rotaviruses, Torovirus, Adenoviruses, Caliciviruses, Astroviruses, and a group of Norwalk-like viruses.

Viral gastroenteritis is NOT caused by any of the following, although the symptoms may be similar:

  • bacteria such as Salmonella or E. coli

  • parasites such as Giardia

  • medications

  • other medical conditions

Diarrhea and vomiting are the main symptoms of viral gastroenteritis

The main symptoms of viral gastroenteritis are:

  • diarrhea

  • vomiting

A child with viral gastroenteritis may also have:

  • headache

  • fever

  • stomach cramps or a sore stomach

In general, the symptoms begin 1 to 2 days after catching the virus. They can last for 1 to 10 days.

Viral gastroenteritis can be spread

Viral gastroenteritis can spread through the following methods:

  • sharing food, water, or eating utensils such as forks and knives with someone who has the virus

  • not washing hands after touching items that may have the virus on their surface

Anyone can catch viral gastroenteritis

People of all ages and backgrounds can get viral gastroenteritis. However, different groups often get different viruses:

  • Babies and toddlers tend to get Rotaviruses and Torovirus more often.

  • Adenoviruses and Astroviruses tend to cause diarrhea mostly in young children.

  • Norwalk-like viruses are more likely to cause diarrhea in older children and adults.

Treating viral gastroenteritis

The most important way of treating viral gastroenteritis in children and adults is to prevent dehydration. Dehydration means severe loss of fluids. Ask your doctor how to prevent dehydration if your child has the symptoms.

Symptoms of dehydration include:

  • dry or sticky mouth

  • thirst

  • low or no urine output; concentrated urine appears dark yellow

  • not producing tears

  • being irritable or cranky

  • seeming bored or uninterested

  • headache

  • dizziness

  • cramps

  • chills

  • fatigue

In severe cases, dehydration can cause:

  • sunken eyes

  • sunken fontanelle (soft spot) on the top of a baby's head

  • nausea or vomiting

  • lethargy or coma

If your child becomes very dehydrated, your child may have to be treated at the hospital. In the hospital, fluids can be replaced through an intravenous line (IV) if necessary.

You can prevent viral gastroenteritis with good hand washing

To avoid catching or spreading viral gastroenteritis, you should do the following things:

  • Wash hands well and often. This is especially important at hospitals and other medical facilities.

  • Do not visit anyone in hospital when you are ill with symptoms of viral gastroenteritis. Ask other family members and friends to do the same.

If your child is in hospital, help stop viral gastroenteritis from spreading

  • Your child may be placed in a single room and will not be able to visit the playroom until they are feeling better. Ask the Child Life Specialist to bring toys and supplies to your child's room.

  • Wash your hands often before and after touching your child and before leaving your child's room. Expect hand washing by hospital staff as well.

  • If you or anyone else who has visited becomes ill with symptoms of viral gastroenteritis, let your child's doctor or nurse know. 

  • If your child has symptoms of viral gastroenteritis and they are in the hospital, all staff caring for your child should wear gloves and a gown.

Viral gastroenteritis is rarely a serious illness

For most people, viral gastroenteritis is not a serious illness. People who get viral gastroenteritis almost always recover completely without any long-term problems. How fast a child recovers from viral gastroenteritis partly depends on which virus is causing the illness.

Viral gastroenteritis can be a serious illness in people who are unable to drink enough fluids to replace what they lose through vomiting or diarrhea. Babies, young children, and people who are unable to care for themselves, such as the disabled or elderly, are at risk for dehydration from losing too much of the body's water.

People with immune system problems are at risk for dehydration because they may get more severe symptoms than healthy people, and have more vomiting and diarrhea. People with severe symptoms may need to stay in the hospital for treatment to correct or prevent dehydration.

Key points

  • Viral gastroenteritis is an infection of the stomach and intestines.

  • The main symptoms include diarrhea and vomiting.

  • Diarrhea and vomiting can cause a loss of fluids, also called dehydration.

  • If dehydration is severe, patients may have to be given fluid intravenously (IV) at the hospital.

  • Viral gastroenteritis can spread by sharing food, water, and utensils. Frequent hand washing can help prevent the spread of infection to others.

  • Viral gastroenteritis is usually not a serious illness. However, people who have weak immune systems are at risk for more serious infection.

Laurie Streitenberger, RN, BSc, CIC
Anne Matlow, MD, FRCPC