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.
Many different viruses can cause stomach flu, including rotaviruses, adenoviruses, and the Norwalk virus. 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, you might get it by kissing or shaking hands or by sharing food, drink, or eating utensils.
The virus irritates the stomach and intestine. When the stomach and intestine are irritated, they don’t work as well as they should. Food may move faster through your digestive tract.
When you have stomach flu, you may have one or more of the following symptoms:
The illness may develop over a period of hours, or it may suddenly start with stomach cramps, vomiting, or diarrhea.
Some bacteria, parasites, medicines, or other medical conditions can cause similar symptoms. If your symptoms are unusually severe or last longer than a couple days, your healthcare provider can check to see if the diarrhea is caused by something other than a virus.
Your healthcare provider will ask about your symptoms. He or she will examine you. You may have lab tests to rule out more serious illnesses and to check for problems that can be caused by stomach flu, such as dehydration.
The most important thing to do is to rest the stomach and intestine. You can do this by not eating solid food for a while and drinking only clear liquids. As your symptoms go away, you can start eating 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 healthcare provider what sport drinks or other 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. Suck on ice chips or Popsicles if you feel too nauseated to even sip fluids. Avoid liquids that are acidic (such as orange juice) or caffeinated (such as coffee) or have a lot of carbonation. Don’t drink milk until you no longer have diarrhea.
You may start eating soft, plain 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, soft-boiled 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.
If you have cramps or stomach pain, it may help to put a hot water bottle or electric heating pad on your stomach. Cover the hot water bottle with a towel or set the heating pad on low so you don’t burn your skin.
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. Don’t use it for more than 2 days without checking with your healthcare provider. If you have chronic health problems, always check with your healthcare provider before you use any medicine for diarrhea.
Stomach flu rarely lasts longer than 1 to 3 days. However, it may be 1 to 2 weeks before your bowel habits are completely back to normal. It can be a serious illness in people whose immune system isn’t working properly.
Dehydration is a potentially serious complication of stomach flu. It can happen 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.
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.
