Gastroenteritis (“Stomach Flu”)

What is gastroenteritis?

Many people blame “the stomach flu” whenever they fall ill with nausea, diarrhea, or vomiting. But stomach flu is actually a misnomer: The viruses that cause the “real” flu (influenza) usually don’t affect the stomach. When doctors speak of stomach flu, they’re usually referring to a popular name for a condition in which the digestive tract becomes irritated and inflamed. However, they are more likely to use the medical term for this condition: gastroenteritis.

Whatever you call it, gastroenteritis is a very common problem. Up to 100 million cases occur each year in the United States alone. For most healthy people, the condition is a minor illness on a par with the common cold. However, without treatment it can be deadly to the very young, the very old, or the sick and frail. In developing countries, prolonged bouts of diarrhea brought on by gastroenteritis are a leading cause of death.

What causes gastroenteritis?

Most cases are caused by viruses, but not by the same viruses that cause influenza. A leading culprit is rotavirus, a common germ that is easily spread through physical contact, such as shaking hands or sharing eating utensils. Rotavirus is especially likely to show up among young children and in daycare centers.

About one in five people with “stomach flu” has a bacterial infection, often acquired through food poisoning or drinking untreated water. Common bacterial sources of the disease include Salmonella, E. coli, and Campylobacter.

Other possible causes of gastroenteritis include parasites (organisms larger than viruses or bacteria), toxins from tainted shellfish, and reactions to medications (including antibiotics and laxatives). It’s also linked to chronic diseases such as ulcerative colitis or Crohn’s disease.

Because disease-causing bacteria and viruses thrive in areas with poor civic sanitation, gastroenteritis often strikes travelers to developing countries. That’s why between 20 and 50 percent of the people who travel abroad come back with a form of gastroenteritis called traveler’s diarrhea, according to the Centers for Disease Control and Prevention. Domestic travelers should also be wary. Tiny parasites that attack the stomach also live in cold climates in the U.S., and they can be picked up if you drink water while swimming in or camping near rivers and lakes.

What are the symptoms of gastroenteritis?

The main symptom is diarrhea. (The term “stomach flu” owes much of its popularity to the fact that people don’t like to say they have diarrhea.) If caused by an infection, the diarrhea usually begins within a day or two of picking up the germ and lasts up to 10 days. Nausea, vomiting, headache, or abdominal pain often accompanies diarrhea, which doctors define as having more than two loose bowel movements in a day.

When should I see the doctor?

Most cases of gastroenteritis aren’t serious enough to warrant a trip to the doctor. However, you should call your doctor if you notice any of the following signs of trouble:

  • Blood in your stool or vomit
  • High fever
  • Severe, localized stomach pain. You should be especially concerned about pain in the lower right abdomen, a possible sign of appendicitis.
  • An inability to keep food or liquids down, or losing fluids faster than you can replenish them orally
  • Vomiting that becomes more violent or lasts for more than 48 hours
  • Signs of dehydration (dry mouth, dry skin, thirst, no urination for six hours)

What can a doctor do to treat the illness?

Before doing anything else, your doctor will try to confirm the diagnosis by checking your symptoms and conducting a physical. If you’ve recently eaten something that might have spoiled or you’ve visited a place with poor sanitation, be sure to mention it. It would also be good to tell your doctor if you’ve been traveling recently or if you’ve been in contact with someone who has similar symptoms.

Once the condition has been diagnosed, your doctor can start treating the symptoms.

Doctors may suggest a bland diet (although the scientific data to suggest this is sparse), and frequent small amounts of fluids, possibly including rehydrating fluids to treat dehydration. Rehydrating fluids are a special mix of water, sugar, and salts available in pharmacies that replace the water you lost. In extreme cases, the fluid may be given intravenously.

If you have severe diarrhea, your doctor may advise you to take an over-the-counter drug that slows down intestinal function and prescribe an anti-nausea drug as well. If you have been experiencing the symptoms for only a few days and the symptoms are relatively mild, your doctor will most likely suggest you try to treat the symptoms and avoid antibiotics.

If the illness is severe or lingers for more than a couple of weeks, your doctor may want to collect a stool sample to pinpoint the exact cause of the distress.

What should I do if I have the condition?

Most people with gastroenteritis just need to rest for a few days. If vomiting is a problem, you have to avoid certain solid foods for a while. As soon as you feel up to it, sip small amounts of clear liquids such as tea or broth every 15 minutes. As your stomach starts to settle down, you can move on to solid food.

Because children with diarrhea can get dehydrated very easily, they may need special care. Give sick children plenty of liquids — offering a small amount of liquid every few minutes or so, even if they are vomiting. Infants who seem restless or unusually thirsty should be given an oral rehydration solution, water mixed with a packet of salt and carbohydrates; they are also sold in bottles (e.g. Pedialyte and Ricelyte). These packets and rehydrating liquids are widely available in supermarkets and drug stores and are even sold in popsicle form. Don’t give children carbonated beverages or sports drinks. A child who needs to take these liquids for more than a day or two should probably see the doctor to be sure that he or she is not getting dehydrated.

Can the condition be prevented?

Because most cases are caused by bacteria or viruses, you can prevent much misery by taking a stand against germs. First and foremost, make sure everyone in your house washes his or her hands regularly, especially after using the bathroom and before touching food. Hand washing becomes even more important when someone in the house is having a bout of gastroenteritis.

You should also take steps to prevent food poisoning. Keep your kitchen clean, carefully watch expiration dates on food, and don’t leave perishable food at room temperature for more than two hours. Be extra careful with raw chicken, a major source of Campylobacter, or any raw meats or eggs, for that matter. Clean any surfaces and kitchen tools that you use to handle raw chicken with soap and hot water before preparing another dish.

Before you leave on a trip, it’s a good idea to visit your doctor to talk about what you can do to prevent problems with diarrhea when you are traveling in areas with poor sanitation. Among other things, you can get immunized against typhoid, hepatitis A, and other illnesses. Your doctor may also advise you to travel with Pepto Bismol, which has some antibacterial activity. Or he may recommend an antidiarrheal medication that can help you if you’re stuck on a long bus ride in with no bathroom readily available or suggest prophylactic antibiotics in case you are somewhere without a doctor.

And if you’re traveling to an area with poor sanitation, don’t trust the water. Simply brushing your teeth with tap water or tossing a couple of ice cubes in a drink can be enough to make you sick. In many areas, the only safe beverages are boiled or bottled water, canned or bottled sodas, tea and coffee made with boiled water, beer, and wine. If it’s not possible to boil your water, you may have to use chemical disinfectants such as iodine or chlorine.

Keep in mind that the food can be as risky as the water. You should be especially suspicious of salads, garnishes, uncooked vegetables, unpasteurized milk, raw meat, shellfish, and any foods sold by street vendors. In general, fruits that you peel yourself and hot meals are safer choices. (Some restaurants in developing countries that cater to tourists disinfect their lettuce and other vegetables before making them into salads, but salads sold on the street may not be.)

Since 2008, the American Academy of Pediatrics has recommended a rotavirus vaccine for all infants. Two vaccines given orally, not by a shot, are licensed for use in the United States: RotaTeq (RV5) is given in 3 doses at ages 2 months, 4 months, and 6 months; Rotarix (RV1) is given in 2 doses at ages 2 months and 4 months.

In general, if you want to help keep “stomach flu” at bay, soap and water is one of the best defenses. Use them often. Your stomach will thank you.


Parashar, Umesh, D., Alexander, James P., et al Prevention of rotavirus, gastroenteritis among infants: Recommendations of the Advisory Committee on Immunization Practices, Division of Viral Diseases, National Center for Immunization and Respiratory Diseases (proposed), Morbidity and Mortality Weekly Report, 55(RR12);1-13

Centers for Disease Control and Prevention. Viral gastroenteritis.

Centers for Disease Control and Prevention. Travelers’ Diarrhea.

Cleveland Clinic. Gastroenteritis.

Merck Manual of Diagnosis: Gastroenteritis.

Bonheur, Jennifer L., MD, et al. Gastroenteritis, Bacterial. eMedicine.

Diskin, Arthur, MD. Gastroenteritis. eMedicine, Vol. 3, no. 4,

Merck Manual. Gastroenteritis. September 2007.

The Childrens Hospital of Philadelphia. Are vaccines safe?

© HealthDay

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