Stomach Flu (Gastroenteritis)

Gastroenteritis is an infection of the stomach and intestines.   Most often, it is caused by a virus, but some cases may be bacterial or parasitic in origin.  The terms “stomach flu” or “intestinal flu” specifically refer to gastroenteritis caused by a virus.  Although symptoms may vary from person to person, it is generally associated with nausea, vomiting, stomach cramping, and watery diarrhea.  A person may experience all of these symptoms, or may just have one or two.  It is important to know that, despite being called “stomach flu, ” this infection is unrelated to the influenza virus that causes seasonal flu.  In addition, the annual flu vaccine does not protect against viral gastroenteritis.  In most cases, “stomach flu” is not serious in healthy individuals.  In infants, children, the elderly, and those who are immunocompromised, however, gastroenteritis can cause life threatening dehydration and electrolyte imbalances.

Causes of Viral Gastroenteritis

Most cases of gastroenteritis are caused by community acquired viruses.  In adults, it is frequently caused by Norwalk virus and adenovirus, but rotaviral infections are more common in infants and children.  However, because these viruses are quite contagious, they can easily spread to all members of a household.

These infections are the reason for over 200,000 hospitalizations and 300 deaths in infants and children in the U.S. each year.  The virus is shed in the stool, so it can easily be transmitted to others during diaper changes or toileting. Daycare centers and schools are known to have outbreaks.  Other congregate settings such as cruise ships and senior care homes are sources of these infections in older children and adults.

Symptoms of Gastroenteritis (Stomach Flu)

The primary symptom of viral gastroenteritis is watery diarrhea, but other possible symptoms include:

  • nausea and vomiting
  • stomach cramps or bloating
  • chills and fever
  • loss of appetite
  • over-all weakness

If symptoms are severe enough to cause dehydration, there may be 

  • lightheadedness
  • dry mouth or lips
  • lethargy or reduced responsiveness
  • less frequent or no urination
  • a sunken fontanelle (soft spot) in infants

How Do You Get Gastroenteritis (Stomach Flu)?

Viral infections are spread from person to person through physical contact, or by contact with objects an infected person may have touched.  Specific to gastroenteritis, there is either direct contact with fecal material, or ingestion of  contaminated food or water.  The chances of catching such viruses is increases in locations where there are crowds of people such as offices, shopping malls, daycare centers, schools, churches, or recreational events.  Individuals who have weakened immune systems are particularly at risk.  In the past, increased numbers of cases were seen during cold weather months, but gastroenteritis now seems to occur year round.

The best way to prevent a case of “stomach flu” is to avoid contact with anyone who has symptoms, and to wash your hands before eating or drinking.  Here are a few ways to reduce your chances of becoming ill:

  • Use proper hand washing techniques after any contact with stool (i.e. using the restroom, changing diapers, assisting others with toileting).
  • Don’t share food, beverages, or utensils with anyone who has symptoms of stomach flu.
  • If someone in your family has symptoms, if possible, have this person use a separate bathroom until they are well.  This bathroom should be sanitized with a disinfectant once the illness resolves.  If this is not possible, then the bathroom should be cleaned and disinfected each time the person with gastroenteritis uses it.
  • Avoid touching surfaces that someone with symptoms has touched, especially wet surfaces in bathrooms and kitchens.
  • Anyone who has symptoms should not prepare or handle the food or beverages of others.  This includes workplaces such as restaurants and school cafeterias.

Treating Gastroenteritis (Stomach Flu)

In most cases, care at home is usually all that is needed.  You will want to be where there is quick access to a bathroom or  bedpan.  If vomiting is part of the illness, it typically resolves within 24 hrs, followed by two to three days of diarrhea.  While symptomatic, it is important to modify the diet to prevent exacerbation of symptoms and dehydration.  During the nausea and vomiting phase, small but frequent sips of clear fluids are better tolerated than larger volumes which may trigger further vomiting.  Solid foods may be re-introduced once vomiting becomes less frequent or resolves.  It is often helpful to replace lost electrolytes with oral rehydration beverages.

If, despite these measures, you become dehydrated, it may be best to go the emergency room.  Fluids can be administered intravenously to correct the dehydration, and quickly restore the body’s electrolyte balance.  More serious causes of your symptoms can also be ruled out.  Dehydration, especially in children, older adults, or people with diabetes, can be very serious and require special treatment.  Although symptoms may resolve quickly, you may feel weak for a few more days.  If the diarrhea has not resolved within seven days, non-viral causes must be considered, and it is best to consult a doctor.

Because viral gastroenteritis is not caused by bacteria, antibiotics are ineffective.  All that can be done is to manage the symptoms until the virus clears your gastrointestinal tract.  The best way to “treat” gastroenteritis is to let your body’s immune system fight the virus; as your mom would say, “let it run it’s course.”  While recovering, it is best to avoid foods that further irritate the intestines such as greasy foods and fruit juices.  These can increase or prolong the diarrhea.  Rotavirus and Norwalk viral infections are also known to cause a temporary lactose-intolerance, so avoiding foods with lactose can also be helpful.  

Getting plenty of rest and fluids speeds your recovery, and prevents dehydration.  If you feeling more energetic, it’s OK to do light activities.  However, it is better to rest until any fever, nausea, and vomiting are better.  Staying home from work or school can prevent the spread of the infection to others.

In general, medicines are unnecessary, and can be harmful for infants and children.  In severe cases of vomiting, a doctor may prescribe an anti-nausea medication for children for whom the diagnosis of viral gastroenteritis is certain.  Adults may try one of several over-the-counter antinausea or antidiarrheal medications.  Pepto-Bismol is a common used option;  be aware, however, that it can cause a black discoloration of the tongue and stools.  Imodium or Kaopectate can reduce diarrhea, but adults should consult a doctor if there is no improvement after a few doses.  Antidiarrheals are not recommended for infants and children because they delay the virus leaving the gastrointestinal tract, and can prolong symptoms of illness.  All of these medications are available without a prescription and at your local pharmacy.  Medicines should always be taken per the package’s or a doctor’s instructions.  Be sure to closely follow a doctor’s directions if you are pregnant, or have chronic illness such as diabetes or heart disease.

For cases of diarrhea that last one week or longer, probiotics may be recommended.  Probiotics help to restore the normal gut flora which may have been disrupted due to the infection.  Replacing any lost “healthy bacteria” can reduce the duration of diarrhea.

What you should eat and drink

In some cases of “stomach flu,” the infected person feels nauseous or even vomits.  After an episode of vomiting, it is best to allow the stomach to “rest” for an hour before attempting to drink fluids.  Then, take small sips of clear fluids or ice chips.  Once this is tolerated, slowly introduce more fluids.  Start with a few ounces (a half cup) at a time.  Good options for adults are electrolyte-enhanced waters, coconut water, and sports beverages such as Gatorade or Powerade.  Infants should continue breastfeeding, but a doctor may recommend the temporary use of a lactose-free infant formula for those who are formula fed.  Pedialyte may be recommended for toddlers and older children.

Once you are able to tolerate these liquids, continue drinking them for at least four to eight hours while gradually increasing the amount.  When no further vomiting occurs, it is ok to begin eating bland, solid foods like toast, jello, chicken soup, or crackers.

In addition, fluids with electrolytes are very important to replace the potassium, bicarbonate, and chloride lost in diarrhea. Carbonated beverages, those with caffeine, and fruit juices are not appropriate.  In the absence of vomiting, early introduction of food helps to speed recovery.  Start by eating complex carbohydrates (rice, wheat, potatoes, bread, cereal) and lean proteins such as meats, tofu, chicken, or fish.  Avoid foods that are high in sugar and fat for several days.  If diarrhea persists longer than expected, it may be helpful to eliminate milk and other foods with lactose until the diarrhea resolves.

Preventing the Spread of Stomach Flu

Viral gastroenteritis is a communicable disease.  It is spread through touch, followed by inadvertent ingestion of the virus. These viruses spread very easily by close contact with an infected person.  The best way to prevent the spread of gastroenteritis is to stay away from other people while ill.  At home, avoid sharing any items that you use with others in the household.  Take precautions while cleaning up infected fluids by wearing rubber gloves, and using disinfectants.  Most importantly, wash your hands frequently.

When to Call Your Doctor

Call your regular doctor if:

  • Your diarrhea lasts longer than 3 days.
  • Your symptoms become worse with treatment instead of better.
  • You have diarrhea with mucous or blood.
  • Your symptoms develop after returning from travel outside of the country.
  • Medicines are not helping to controlling nausea or diarrhea.
  • The nausea prevents you from taking your daily medicines for other health conditions.

Go to the emergency room if:

  • You have been vomiting for more than two days or vomiting blood.
  • You have severe abdominal cramps, nausea, vomiting, and fever.  This could be a sign of appendicitis.
  • When you’re having symptoms of dehydration such as weakness, lightheadedness, dizziness, decreased urination, or heart palpitations.

In Summary

  • The symptoms of gastroenteritis vary from person to person, but it is usually associated with nausea, vomiting, and diarrhea.
  • There is no treatment for the viruses that cause gastroenteritis;  only the symptoms can be treated.
  • The body’s immune system fights these viruses, so plenty of rest helps with recovery.
  • To reduce nausea and vomiting, avoid drinking for one hour, then gradually sip caffeine-free fluids that contain electrolytes.  Most solid foods should be avoided for at least 24 hours, but it is fine to try eating crackers, jello, or chicken broth.
  • To prevent dehydration from diarrhea, it is important to replace electrolyte losses with appropriate fluids.  Fruit juices should be avoided as well as foods that are oily or high in sugar.  Other solid foods, however, help stools become more solid, and shorten the length of time it takes for diarrhea to resolve.  “Binding foods” such as bananas, plantains, and rice are particularly helpful.
  • Viral gastroenteritis is a communicable disease. Close contact with anyone who has symptoms should be avoided.
  • If symptoms persist for more than three days or become worse with treatment, call your doctor or go to the emergency room.


Gastroenterology is the branch of medicine that manages disorders of the digestive system.  This includes the organs and glands from mouth to anus.

Below is a list of procedures that are performed by a gastroenterologist.

  • Colonoscopy
  • Gastrostomy
  • Endoscopy
  • Laparoscopy
  • Rectal or Colon Polyp Removal

Leah Alexander, MD, FAAP
Leah Alexander, MD, FAAP

Dr. Alexander began her pediatric career at Elizabeth Pediatric Group of New Jersey in 2000, and has practiced at Pediatricare Associates of New Jersey since 2005. After graduating from Kalamazoo College and Michigan State University College of Human Medicine, she completed her pediatric training at Overlook and Morristown Memorial Hospitals. She is board certified in General Pediatrics. In addition to pediatrics, Dr. Alexander pursued her interest the culinary arts with study at the French Culinary
Institute. In 2007, she opened Global Palate, LLC, catering small group events for six years. Dr. Alexander has also been a professional writer and editor since 2018, engaging in a variety of medical editing and writing projects.