Viral Gastroenteritis (Stomach Flu)

Medically Reviewed By William C. Lloyd III, MD, FACS
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What is viral gastroenteritis (stomach flu)?

Viral gastroenteritis, sometimes called stomach flu, occurs when a virus infects the lining of the stomach, small intestine, or large intestine. It causes inflammation and irritation in the digestive tract, which can lead to stomach pain, vomiting and diarrhea. Viral gastroenteritis can last anywhere from two days to a week.

Anyone can get viral gastroenteritis, and people who are living or eating near lots of other people have a higher risk of getting the illness because it is very contagious. Young children in daycare centers and older adults in nursing homes have a higher likelihood of coming down with stomach flu. People with compromised immune systems also have a greater chance of getting viral gastroenteritis.

Symptoms typically show up within one or two days of becoming infected with a virus that causes stomach flu. The most common viral gastroenteritis symptoms include nausea, vomiting, and diarrhea. Many people with stomach flu also have body aches and fever.

Viral gastroenteritis treatment focuses on rest and keeping the body hydrated, since dehydration is common with stomach flu infection. Untreated, dehydration can get worse quickly, and severe dehydration can sometimes be fatal. It’s important to frequently drink sips of water and other fluids, especially those with electrolytes, to keep the body hydrated while you recover from stomach flu.

What are the symptoms of viral gastroenteritis (stomach flu)?

Most people start experiencing symptoms a day or two after becoming infected with a virus that causes stomach flu. While viral gastroenteritis symptoms may be intensely unpleasant, they aren’t life threatening and typically don’t need treatment.

However, dehydration caused by vomiting and diarrhea can be serious and can worsen very quickly. Anyone with viral gastroenteritis should drink extra fluids and be alert to signs of dehydration.

Common symptoms of viral gastroenteritis

The most common viral gastroenteritis symptoms are:

Signs of dehydration

Extreme thirst is a sign that you may be dehydrated, but there are also many other signs. Keep in mind, signs of dehydration may be different in young children vs. adults. In addition to thirst, typical signs of dehydration include:

Signs of dehydration in young children:

  • Dry diapers for more than 3 hours, or fewer than 6 wet diapers a day

  • Crying without any tears

  • Unusual drowsiness

  • Sunken eyes, cheeks, or soft spot on a baby’s head

While viral gastroenteritis doesn’t typically need medical treatment, dehydration can be serious and must be treated. Mild dehydration can be treated by sipping extra fluids or by sucking on ice pops. Closely monitor a baby’s diapers to ensure they’re wetting normally. Someone with moderate to severe dehydration should go to the hospital for treatment.

Signs of moderate to severe dehydration

Severe dehydration is a medical emergency and can be fatal. If you or your child have signs of dehydration that don’t improve by drinking extra fluids, seek immediate medical attention. Signs of moderate to severe dehydration include:

Signs that you should see a doctor

While you don’t necessarily need to see a doctor for general viral gastroenteritis symptoms, certain signs indicate you do need to call your healthcare provider. These signs include:

  • High fever

  • Bloody or tarry stools

  • Severe pain

  • Inability to keep any fluids down due to vomiting

  • Signs of dehydration that don’t improve with extra fluids

  • Persistent symptoms that last more than a week or two

What causes viral gastroenteritis (stomach flu)?

Many kinds of viruses can cause stomach flu; however, the influenza virus, which causes the seasonal flu, isn’t one of them. A few of the viruses that cause viral gastroenteritis include:

  • Rotavirus, which typically affects children under 2 years old

  • Enteric adenovirus, which typically affects children under 2 years old

  • Astrovirus, which often affects children under 3 years old

  • Norovirus, which typically affects adults

What are the risk factors for viral gastroenteritis (stomach flu)?

While anyone can get viral gastroenteritis, young children and older adults are at the highest risk of getting stomach flu.

Other risk factors include a compromised immune system or traveling to a developing country. Additionally, certain environments put people at a higher risk of passing around viruses that cause stomach flu. Anywhere that many people live or eat together is a place that’s likely to host viral gastroenteritis germs.

These high-risk places include:

  • Schools and daycare centers 

  • Children’s camp

  • Nursing homes

  • Dorms and residence halls

  • Public gatherings where food is served buffet style

  • Military dining facilities

  • Prisons

  • Cruise ships

If you live in or frequently visit a high-risk environment, take extra precautions to stay healthy. For example, don’t share food or drinks with others. Also, wash your hands frequently and use hand sanitizer when you don’t have access to soap and water.

How do you prevent viral gastroenteritis (stomach flu)?

While viruses are everywhere, you can take steps to reduce your risk of becoming infected. For example:

  • Don’t share food, drinks, or eating utensils with others, especially someone who may be sick.

  • Wash your hands for 20 seconds with soap and water after going to the bathroom and before eating.

  • Use alcohol-based hand sanitizer.

  • Sanitize frequently touched surfaces regularly. 

  • Disinfect cooking and eating areas regularly. 

  • Don’t touch your face.

  • Stay away from anyone who is showing symptoms of illness.

  • Vaccinate infants against rotavirus.

If you or someone in your household is sick with viral gastroenteritis, stay home and away from others until you are symptom-free. Disinfect any areas where someone who was sick has been, especially bathrooms. Wash laundry, sheets, and towels in hot water.

How do doctors diagnose viral gastroenteritis (stomach flu)?

Your doctor will most likely be able to diagnose viral gastroenteritis based on your symptoms. Testing isn’t usually needed, unless symptoms don’t resolve on their own. In this case, your doctor may want to test your stool for viruses, bacteria, or parasites.

How do you treat viral gastroenteritis (stomach flu)?

Because viral gastroenteritis is caused by a virus, there’s no medicine to cure the condition; the sickness simply has to run its course through your system.

Treatment for viral gastroenteritis focuses on preventing dehydration. Because your body may lose a lot of electrolytes (such as sodium and potassium) due to diarrhea or vomiting, drinking just water may not be enough to prevent dehydration. Sports drinks can help replace lost electrolytes for adults and older children, but they also contain a lot of sugar, so drink them in moderation.

While you might be tempted to take an over-the-counter medication for upset stomachs, such as bismuth subsalicylate, it’s best to talk with your doctor first, especially if you have a high fever or bloody stools. These medications are never safe for children.

Viral gastroenteritis at-home care

Treatment of viral gastroenteritis is intended to help prevent complications such as dehydration. You can treat symptoms and prevent complications of viral gastroenteritis at home by:

  • Getting plenty of rest

  • Frequently drinking small amounts of extra fluids, such as water, sports drinks, and ice pops 

  • Sipping an oral rehydration solution or sucking on special ice pops, especially for young children

  • Eating small amounts of easy-to-digest foods, such as crackers or broth, when you feel up to eating

  • Avoiding milk, alcohol, and caffeine 

If you or your child cannot keep fluids down, call your doctor. You may need intravenous (IV) fluids to prevent dehydration.

What are the potential complications of viral gastroenteritis (stomach flu)?

While viral gastroenteritis isn’t a life threatening illness, the symptoms of vomiting and diarrhea can cause dehydration, which can be serious in some cases. While it can often be prevented by sipping extra fluids, dehydration can get worse if lost fluids aren’t replaced. Moderate to severe dehydration can be fatal, and these conditions should be treated at a hospital.

Complications of severe dehydration

Without medical treatment, severe dehydration can lead to:

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Medical Reviewer: William C. Lloyd III, MD, FACS
Last Review Date: 2020 Dec 16
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THIS TOOL DOES NOT PROVIDE MEDICAL ADVICE. It is intended for informational purposes only. It is not a substitute for professional medical advice, diagnosis or treatment. Never ignore professional medical advice in seeking treatment because of something you have read on the site. If you think you may have a medical emergency, immediately call your doctor or dial 911.
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