Intestinal Flu

Medically Reviewed By William C. Lloyd III, MD, FACS
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What is intestinal flu?

Intestinal flu is a viral infection of the gastrointestinal tract. The medical name is viral gastroenteritis, and other common names include stomach flu, or a 24-hour or 48-hour “bug.” It is the second most common illness affecting American families. Intestinal flu involves irritation and inflammation of the gastrointestinal tract and is not actually a form of flu or influenza.

The hallmark symptoms of intestinal flu are nausea, vomiting and diarrhea. Similar gastrointestinal symptoms involved with intestinal flu can also result from a variety of other conditions, such as bacterial food poisoning, alcohol intoxication, and irritable bowel syndrome. Intestinal flu is often mistaken for these other conditions and vice versa.

Symptoms of true intestinal flu or viral gastroenteritis often subside within 24 to 48 hours if you refrain from eating solid foods and get plenty of fluids. If intestinal flu causes serious dehydration, hospitalization and rehydration with intravenous fluids may be necessary.

Intestinal flu is quite common and extremely contagious. It can occur in any age group or population. It tends to affect infants, children, the elderly, and people with compromised immune systems more seriously than healthy adults.

Intestinal flu can lead to serious complications, such as dehydration. Seek prompt medical care if you have a chronic illness, a compromised immune system, or symptoms of intestinal flu that do not improve after a day or two. Contact your physician or health care provider right away if your newborn baby has symptoms of intestinal flu.

Seek immediate medical care (call 911) if you, your child, or someone you are with, have symptoms of intestinal flu accompanied by lethargy, change in alertness, inability to produce tears, major rectal bleeding, or lack of urination.

What are the symptoms of intestinal flu?

The symptoms of intestinal flu can range from mild to severe and may vary depending on the underlying viral infection. The symptoms generally resolve within 24 to 48 hours but may last up to 10 days.

Symptoms of intestinal flu can include:

Serious symptoms that might indicate a life-threatening condition

Intestinal flu can lead to serious or life-threatening dehydration. Seek immediate medical care (call 911) if you, your child, or someone you are with, have any of the following symptoms:

  • Change in alertness or consciousness such as passing out

  • Delirium

  • Extreme thirst

  • Inability to drink and hold down fluids

  • Lack of urination or fewer wet diapers in infants

  • Lethargy

  • Major rectal bleeding

  • Shallow, raspy, or difficulty breathing

  • Sunken fontanel (soft spot) in infants

  • Unresponsiveness

What causes intestinal flu?

Intestinal flu is caused by a gastrointestinal viral infection. These infections can be transmitted by contact with people who have intestinal flu, or by ingesting water or food contaminated with a gastrointestinal virus.

Common types of viruses that cause intestinal flu and gastroenteritis include:

  • Adenovirus

  • Astrovirus

  • Norovirus (90% of all USA cases)

  • Rotavirus (most commonly affects children under the age of five)

Other conditions with symptoms similar to those of intestinal flu

Symptoms similar to those of intestinal flu can also result from a variety of other conditions including:

  • Alcohol intoxication

  • Anthrax infection

  • Bacterial gastrointestinal infection, such as Salmonella food poisoning, Campylobacter infection, or traveler’s diarrhea

  • Dysentery (bloody, watery stools often caused by Shigella and E. coli bacteria)

  • Indigestion

  • Irritable bowel syndrome (IBS; digestive discomfort that does not cause intestinal damage or serious disease)

  • Medication side effects

  • Parasite infections such as Giardia

  • Stress

  • Toxic ingestion, such as eating poisonous plants, mushrooms or chemicals

What are the risk factors for intestinal flu?

A number of factors increase the risk of developing intestinal flu. They include:

  • Close contact with a person who has viral gastroenteritis

  • Close contact with pet feces, reptiles, and foods potentially contaminated with intestinal viruses

  • Crowded conditions, such as in dormitories or on cruise ships

  • Weakened immune system due to such conditions as HIV/AIDS, diabetes, kidney disease, or cancer or cancer treatment

People most at risk of intestinal flu-related dehydration

Dehydration is a common complication of intestinal flu and can be life threatening in some age groups and populations. People most at risk of dehydration from intestinal flu include:

  • Infants and young children

  • People with chronic illnesses, such as diabetes or cancer

  • People with suppressed immune systems due to such conditions as HIV/AIDS, taking chemotherapy, or taking steroid medications

  • Those ages 65 and older

Reducing your risk of intestinal flu

Not all people who are at risk of intestinal flu will develop the condition, but you can lower your risk of developing or transmitting viral gastroenteritis by :

  • Avoiding contact with a person who has intestinal flu or its symptoms, such as vomiting and diarrhea

  • Washing your hands frequently and especially after using the restroom, before eating, and during and after contact with a person who has intestinal flu or its symptoms, such as vomiting and diarrhea

How is intestinal flu treated?

Rehydration is the cornerstone of treatment for intestinal flu for all age groups and types of viral infections. Treatment plans also generally involve rest and minimizing the discomfort of nausea, vomiting and diarrhea.

Treatment of intestinal flu may include:

  • Avoiding solid foods to rest the stomach and intestines until symptoms have passed

  • Drinking plenty of fluids (water or rehydrating fluid such as Pedialyte) to ensure adequate hydration

  • Hospitalization and rehydration with intravenous fluids if the intestinal flu does not resolve quickly or leads to dehydration

What are the potential complications of intestinal flu?

Complications of intestinal flu can be serious and life threatening in some cases. Complications can include:

  • Aspiration, which is when contents of the stomach flow into the lungs during vomiting (a rare occurrence)

  • Severe dehydration, which can lead to an electrolyte imbalance and shock

  • Torn esophagus (Mallory-Weiss tear) due to multiple violent episodes of retching and vomiting (a rare occurrence)
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Medical Reviewer: William C. Lloyd III, MD, FACS
Last Review Date: 2020 Dec 19
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THIS TOOL DOES NOT PROVIDE MEDICAL ADVICE. It is intended for informational purposes only. It is not a substitute for professional medical advice, diagnosis or treatment. Never ignore professional medical advice in seeking treatment because of something you have read on the site. If you think you may have a medical emergency, immediately call your doctor or dial 911.
  1. Viral Gastroenteritis. The Centers for Disease Control and Prevention.
  2. Viral gastroenteritis. PubMed Health, a service of the NLM from the NIH.
  3. Norovirus. The Centers for Disease Control and Prevention.
  4. Collins RD. Differential Diagnosis in Primary Care, 5th ed. Philadelphia: Lippincott, Williams & Williams, 2012.