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Stomach Flu (Viral Gastroenteritis)

What is stomach flu?
Stomach flu is a viral infection that affects the stomach and small intestine. It is also called viral gastroenteritis. The illness is usually brief, lasting 1 to 3 days.

How does it occur?
Many different viruses can cause gastroenteritis, including rotaviruses, adenoviruses, and the Norwalk virus. Gastroenteritis is caused by swallowing one of these viruses. The body fluids of infected people contain the virus, sometimes even before their symptoms begin. The virus can be spread by direct contact with an infected person (for example, kissing or shaking hands) or by sharing food, drink, or eating utensils.

The virus enters the stomach and intestine and inflames the lining of these organs. As a result, the stomach and intestine are temporarily unable to perform their usual functions. The virus can also cause food to move more rapidly through your gastrointestinal (GI) tract.

Some bacteria, parasites, medicines, or other medical conditions can cause infections that have symptoms similar to those of stomach flu. If your symptoms are unusually severe or last longer than a few days, your health care provider can determine if the diarrhea is caused by something other than a virus.


What are the symptoms?
When you have stomach flu, you may have one or more of the following symptoms:

  • nausea
  • vomiting
  • stomach cramps
  • diarrhea
  • mild fever
  • fatigue
  • chills
  • loss of appetite
  • muscle aches

The illness may develop over a period of hours, or it may suddenly start with stomach cramps, vomiting, or diarrhea.

How is it diagnosed?
Your health care provider will review your symptoms. He or she may examine you and order lab tests to rule out more serious illnesses, such as appendicitis, and to detect complications, such as dehydration.

How is it treated?
The most important thing to do is to rest the stomach and intestines. You can do this by first eating nothing solid and drinking only clear liquids. A little later you can eat soft bland foods that are easy to digest.

If you have been vomiting a lot, it is best to have only small, frequent sips of liquids. Drinking too much at once, even an ounce or two, may cause more vomiting. Your choice of liquids is important. If water is the only liquid you can drink without vomiting, that is OK. However, if you have been vomiting often or for a long time, you must replace the minerals, sodium and potassium, that are lost when you vomit. Ask your health care provider what sport drinks or other oral rehydration drinks could help you replace these minerals.

Other clear liquids you can drink are weak tea and apple juice. You may also drink soft drinks without caffeine (such as 7-UP) after letting them go flat (lose their carbonation). It may be easier to keep down liquids that are cold. Avoid liquids that are acidic (such as orange juice) or caffeinated (such as coffee) or have a lot of carbonation. Do not drink milk until you no longer have diarrhea.

You may start eating soft bland foods when you have not vomited for several hours and are able to drink clear liquids without further upset. Soda crackers, toast, plain noodles, gelatin, eggs, applesauce, and bananas are good first choices. Avoid foods that are acidic, spicy, fatty, or fibrous (such as meats, coarse grains, vegetables). Also avoid dairy products. You may start eating these foods again in 3 days or so, when all signs of illness have passed.

Sometimes treatment includes prescription medicine to prevent nausea and vomiting or diarrhea. Nonprescription medicine is available for the treatment of diarrhea and can be very effective. If you use it, make sure you use only the dose recommended on the package. If you have chronic health problems, always check with your health care provider before you use any medicine for diarrhea.

If you have been vomiting for more than a day or have had diarrhea for over 3 days, call your health care provider. You may need to have an exam to rule out more serious problems and to check for dehydration. You may also need to have lab tests to determine whether bacteria or germs such as Giardia are causing your illness. Dehydration is a potentially serious complication of stomach flu. It can occur if your body loses too much fluid because you keep vomiting or having diarrhea. If you are severely dehydrated, you may need to be given fluids intravenously (IV). In children and older adults, dehydration can quickly become life threatening.


How long do the effects last?
Stomach flu rarely lasts longer than 1 to 3 days. However, it may be 1 to 2 weeks before your bowel habits return completely to normal.

How can I take care of myself?

  • Rest your stomach and intestines by following the guidelines above, but make sure you prevent dehydration by drinking enough liquids.
  • Drink just small amounts often during the vomiting phase of your illness.
  • Do not take aspirin, ibuprofen, or other anti-inflammatory medicines (NSAIDS) without checking first with your health care provider.
  • Call your health care provider if:
    • Your symptoms are getting worse.
    • You continue to have severe symptoms for more than 1 or 2 days, or you are just not getting better after a few days.
    • You develop symptoms that are not usually caused by stomach flu, such as blood in your vomit, bloody diarrhea, or severe abdominal pain.

What can I do to help prevent stomach flu?
The single, most helpful way to prevent the spread of stomach flu is frequent, thorough hand washing. Also, avoid contact with the body fluids of an infected person, including saliva. Don't share food with someone who has stomach flu.