Stomach Flu (Gastroenteritis)

Overview

What is stomach flu (gastroenteritis)?

Gastroenteritis is inflammation (irritation) of your intestines. People usually call it a “stomach bug” or “stomach flu,” even though it’s not limited to just influenza. Although most people report stomach pain, gastroenteritis can also involve your small intestines and colon.

How common is stomach flu (gastroenteritis)?

Stomach flu is common. More than 20 million people get sick each year in the U.S. with an intestinal upset. Viruses are the most common cause of stomach flu.

Who gets stomach flu (gastroenteritis)?

Anyone can come down with stomach flu. But you’re more likely to get it if you’re in a place where lots of people share living or dining spaces, such as:

  • Children in daycare or at camp.
  • Nursing homes.
  • Students living in dormitories.
  • Military personnel.
  • Prisons.
  • Psychiatric wards.
  • Cruise-ship passengers.
  • Travelers to less-developed countries.
  • Anyone with immune compromised state.

Symptoms and Causes

What causes stomach flu (gastroenteritis)?

You can get sick from bacteria, parasites, toxins and viruses. Viruses are the most common cause of so-called stomach flu. Norovirus is often the culprit for adults, while rotavirus is frequently to blame for stomach flu in children. These viruses mostly infect the lining of the small intestine.

What are the symptoms of stomach flu (gastroenteritis)?

The main symptom of gastroenteritis is diarrhea. When the GI tract becomes infected during gastroenteritis, multiple activities from the virus brings on diarrhea. Malabsorption occurs because of the destruction of the gut cells called enterocytes. The virus can also disrupt the reasbsorption of water and induce secretory diarrhea, which is responsible for the loose liquidy stools.

Can stomach flu cause a fever?

You might get a fever when you have stomach flu. A fever can be a sign that your body is fighting an infection. You may feel sweaty, clammy or have the chills. You may also get a headache or ache all over your body.

Is the stomach flu worse in some people?

In general, most people recover quickly from the stomach flu. Symptoms can be worse in babies, young children, older adults or anyone of any age that is immune-compromised. Vomiting and diarrhea can cause dehydration (not enough water in the body) within just a short period of time, depending on the circumstances. Signs of dehydration include:

  • Extreme thirst.
  • Less urine output than usual (no wet diapers for three hours or more in infants).
  • Urine that is darker in color.
  • Sunken cheeks or eyes.
  • Lightheadedness, dizziness upon standing.
  • General weakness.

Why does stomach flu hit at night?

In some people, the stomach flu symptoms may be more pronounced at night due to their circadian rhythm. At night an increase in immune system activity releases infection-fighting chemicals. These can cause inflammation that make you feel worse as you battle your flu.

Is stomach flu (gastroenteritis) contagious?

Viral stomach flu spreads easily to others. You can catch a stomach flu virus any time of the year, but the common norovirus is more widespread from November to April when people tend to be more indoors. Because a variety of viruses can cause stomach flu, you might get different versions of gastroenteritis many times throughout life.

It’s spread from person to person by coming into contact with tiny, invisible particles from a sick person’s stool or vomit if you:

  • Touch a surface and come in contact with the germs and you touch food or your mouth.
  • Eat or drink food or beverages that have a sick person’s germs.
  • Have close contact with someone who has stomach flu (even if they have no symptoms).

Diagnosis and Tests

When should you see a doctor for stomach flu (gastroenteritis)?

You’ll likely be able to fight off stomach flu virus without seeing a healthcare provider. If you have signs of dehydration (dark, infrequent/low urine output, dry mucous membranes, lightheadedness, dizziness, etc.), you should seek medical care right away. Also call your healthcare provider if you have:

  • High fever.
  • Bloody diarrhea.
  • Severe pain.
  • Symptoms that fail to improve/resolve over time.

How is stomach flu diagnosed?

Healthcare providers often can diagnose stomach flu from your symptoms. But your provider may want to rule out other illnesses with some tests:

  • Stool samples: Tests look for bacteria, viruses or parasites in your stool
  • Sigmoidoscopy: A doctor inserts a thin, flexible tube with a tiny camera from the anus into the lower large intestine to look for signs of inflammatory bowel disease. The sigmoidoscopy is a 15-minute procedure that doesn’t usually require sedation.

Management and Treatment

How can I get rid of stomach flu (gastroenteritis)?

The most important things you can do to feel better faster are rest and staying well hydrated. Between diarrhea and vomiting, your body loses a lot of water and electrolytes. If your belly is still upset, you can take small, frequent sips of water, sports drinks, juice or broth, or chew on ice chips. It is important to know that water alone may not be enough to keep you hydrated in severe cases of diarrhea so make sure to take in electrolyte balance hydration (sports drinks, Gatorade®, Pedialyte®, etc). Eat a normal diet when you feel hungry again.

Prevention

How can stomach flu (gastroenteritis) be prevented?

Since stomach flu can be caused by multiple factors, getting the flu vaccination alone isn’t enough to protect you from gastroenteritis. Children should follow the standard vaccination schedule and get the rotavirus vaccination when indicated. This vaccination can protect your child from getting sick from the rotovirus but not all children can receive this oral vaccination, so please check with your pediatrician before doing so.

You can take other steps to reduce your risk of getting stomach flu:

Practice good handwashing

When you’re sick, the virus spreads from anything that comes in contact with virus-infected feces. Good handwashing is vital in stopping the spread. Viruses left on hands can easily spread to surfaces, food and people you touch. It’s important to wash your hands well after you go to the bathroom, change a diaper, touch any bathroom surfaces and before you handle food.

Be careful with food

You can catch stomach flu from contaminated food or water, or pass it on to someone else. To keep viruses out of your food:

  • Clean kitchen surfaces with a disinfectant (cleaner that kills germs), especially when working with raw meat or eggs.
  • Keep raw meat, eggs and poultry away from foods that are eaten raw.
  • Avoid eating raw or undercooked meat, eggs and shellfish.
  • Consume only pasteurized dairy products and apple juice. Pasteurization is a heating process that kills germs.
  • Rinse fruits and vegetables before eating.
  • Drink bottled water and avoid ice cubes when traveling, especially in developing countries. Unfamiliar germs that live in the water can make you sick.
  • · Stop making food for others when you’re sick and for two days after symptoms are gone.

Clean sick areas

Clean anything that you may have touched while you were sick with stomach flu. Wash laundry with hot water and dry with high heat. Be sure to use a disinfectant to clean areas where a sick person vomited or had diarrhea.

Outlook / Prognosis

How long does stomach flu last?

The stomach flu usually lasts less than a week. Be sure to stay home if you have symptoms, and continue to practice good handwashing afterward. The virus can still be in your stool for up to two weeks after you’ve stopped having symptoms, so be extra careful with your bathroom habits. Always wash your hands after having a bowel movement, and wash any soiled fabrics in hot soapy water.

Living With

What can I do at home to feel better?

Get plenty of rest and keep drinking lots of liquids until your symptoms pass. Drinks that have both sugar and salt (like sports drinks) help your intestine absorb fluids better and replace the lost electrolytes. Nibbling salty crackers along with ginger ale or a similar sweet drink could also help. Avoid dairy products like cow’s milk for one or two days — milk can make diarrhea worse due to temporary lactose intolerance that often come with gastroenteritis.

To control severe diarrhea, your healthcare provider may recommend an over-the-counter medication such bismuth subsalicylate (Pepto-Bismol® or Kaopectate®). You shouldn’t use these medicines if you have a high fever or bloody diarrhea, which can be signs of deeper infection from bacteria or a parasite. Antidiarrheal medications aren’t safe for children to use. Instead, see your healthcare provider for treatment.

Nearly everyone gets a bout of stomach flu at some point. It’s not pleasant, but it usually passes in less than a week. Give yourself time to rest and recover before you go back to your daily activities. Fortunately you can take steps to avoid the likelihood of passing it on to others or picking it up again in the future.

Last reviewed by a Cleveland Clinic medical professional on 04/26/2020.

References

  • American College of Gastroenterology. Diarrheal Diseases — Acute and Chronic. (https://gi.org/topics/diarrhea-acute-and-chronic/) Accessed 11/18/2021.
  • Centers for Disease Control and Prevention. Norovirus. (https://www.cdc.gov/norovirus/) Accessed 11/18/2021.
  • Smolensky, MH. et al. Twenty-four hour pattern in symptom intensity of viral and allergic rhinitis: Treatment implications. (https://www.jacionline.org/article/S0091-6749(95%2970212-1/fulltext) Journal of Allergy and Clinical Immunology. Vol. 95, Issue 5;1084–1096. Accessed 11/18/2021.
  • Merck Manuals. Gastroenteritis. (https://www.merckmanuals.com/home/digestive-disorders/gastroenteritis/gastroenteritis) Accessed 11/18/2021.
  • National Institute of Diabetes and Digestive and Kidney Diseases. Viral Gastroenteritis. (https://www.niddk.nih.gov/health-information/digestive-diseases/viral-gastroenteritis?dkrd=hispt0289) Accessed 11/18/2021.

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