An Overview of the Stomach Flu

Gastroenteritis is the stomach flu infection

Gastroenteritis, which is often called the stomach flu or stomach virus, typically causes an upset stomach, nausea, and diarrhea. The effects can range from mild discomfort to dehydration.

It is usually caused by a viral or bacterial infection, and the diagnosis is based on your clinical symptoms and physical examination. Treatment consists of rest and staying hydrated, but some people need hospitalization and intravenous (IV) fluids.

The stomach flu often resolves on its own within one to three days, but some lingering effects, such as diarrhea and loss of appetite, can last for up to several weeks.


Typically, if you develop the stomach flu, you will notice your symptoms right away. Most people can remember exactly when the effects started and whether it was before, during, or after a meal.

Symptoms of stomach flu may include:

  • Decreased appetite
  • Abdominal pain
  • Diarrhea
  • Nausea
  • Fever
  • Chills
  • Headaches
  • Vomiting
  • Weight loss
  • Feeling dehydrated—a dry mouth or sunken eyes
  • Weakness
  • Muscle Pain and soreness
  • Weight Loss


While mild dehydration is typical with stomach flu, you should watch for signs of severe dehydration, such as dry skin, dizziness, a rapid heart rate, a weak pulse, decreased urine, and dark colored urine.

Young babies who do not wet their diapers for several hours or who have a sunken soft spot on their head may be dehydrated.

While it is rare, severe abdominal infections can spread throughout the body, causing sepsis, which is a dangerous blood infection. Recurrent vomiting and diarrhea can cause and can be caused by bleeding in the gastrointestinal (GI) system.

If you have symptoms that persist longer than 10 days, vomiting that lasts longer than two days, or you have blood in your diarrhea or vomit, you need to contact your doctor and seek medical attention right away.

At-Risk Populations

Adults who are frail or very sick due to other illnesses (such as cancer) may be more susceptible to complications of stomach flu. Small children, similarly, can experience extreme effects of the stomach flu, such as dehydration or a fever-induced seizure.

If you are caring for a child or adult who becomes lethargic (very tired and hard to wake up), confused, or less interactive than usual, you should seek medical advice and attention right away.


The stomach flu is highly contagious. It spreads from person to person through shared utensils, food preparation, touching, and contaminated objects.

Several viruses, including norovirus, adenovirus, and rotavirus commonly cause stomach flu. If you have the viral stomach flu, you may be contagious before your symptoms begin and for several weeks after you recover.

Bacteria like Campylobacter jejuni, E. coli, and salmonella and a variety of parasites can cause the same symptoms— and while their effects are more accurately described as food poisoning, they are also often described as stomach flu, Bacterial and parasitic gastroenteritis infections are often acquired by contaminated food. The illnesses caused by these infections usually last for longer than viral stomach flu and typically don't clear without treatment.

Despite its nickname, the stomach flu is not the flu (influenza). The flu is primarily a respiratory illness and getting a flu shot will not protect against the stomach flu.

Effects of GI Infections

The viral, bacterial, and parasitic infections that cause stomach flu produce a number of effects on the stomach and the intestinal lining. The presence of these organisms triggers a complex process that leads to increased fluid into the GI system. This fluid induces abdominal discomfort, vomiting, and diarrhea. The microorganisms often invade the inner lining, causing pain and microscopic GI bleeding.

As the immune system begins to fight the infection, more fluid and inflammatory cells enter the GI system, causing further discomfort, vomiting, and diarrhea. It takes a few days for all of these effects to resolve as the immune system fights the infection.

When your intestinal lining is inflamed and irritated, your ability to tolerate and digest food diminishes.


Diagnosis of the stomach flu is based on your symptoms. If your symptoms last for more than a few days or if they are more severe than expected, your doctor may advise that you are seen and evaluated. Sometimes additional tests are needed to rule out a more serious problem, especially if your illness is prolonged.

Physical Examination

When you see your doctor, important aspects of your physical examination include a measure of your pulse and blood pressure, as they can be altered if you are severely dehydrated. And your doctor will also do an abdominal examination, using a stethoscope to listen to the sounds that your stomach and intestines make. Stomach flu typically causes active and loud bowel sounds.

Your doctor will also palpate (press on) your stomach to determine whether there is a mass, lump, or area of tenderness, as these findings can be concerning.

Blood Tests

Some blood tests that you may need include a complete blood count (CBC) and electrolyte levels. A CBC may show elevated white blood cells, which is a sign of infection, Electrolyte tests can reflect evidence of dehydration.

Stool Sample

Stool tests are not customary, but if your infection is not resolving, your medical team may need to identify the infectious organism in order to plan out a more effective treatment strategy.

If you have had an unexplained episode of food poisoning, or if there is an outbreak, a stool sample can help identify the cause of your infection.

Imaging Studies

You are not likely to need an imaging test for the evaluation of the stomach flu. However, if you have abdominal distension (enlargement) or if you have severe tenderness on your physical examination, an imaging test such as an abdominal ultrasound or computerized tomography (CT) scan can be helpful. These tests can identify an abnormality such as a bowel obstruction.


Typically, stomach flu can be easily managed at home without medical treatment. If you have frequent watery diarrhea or are vomiting persistently, you may need medical treatment to get rehydrated. 

At-Home Care

It is important to take it easy when you have the stomach flu. Be sure to get enough sleep and to stay comfortable.

To stay hydrated, drink small sips of water or electrolyte drinks once your vomiting stops.

If you feel like eating, keep it bland and simple. Crackers, toast, noodles, and rice are examples of foods that are mild on the stomach and are easy to digest. Avoid greasy, sugary and spicy foods until you are completely back to normal.

You can take Tylenol (acetaminophen) to reduce a fever, but anti-nausea medications are generally not recommended for mild stomach flu.


When you have the stomach flu, it may be contagious to those around you. There are several important strategies you can use to avoid spreading your infection.

  • Wash your hands, especially after using the bathroom or changing diapers, before and after preparing or eating food, and when caring for someone who is sick
  • Use hand sanitizer if soap and water isn't available
  • Wash fruits and vegetables and cook food thoroughly when someone in the house is sick
  • Don't allow sick family members to prepare food or care for others
  • Clean and disinfect surfaces in the home that could be contaminated with the virus
  • Thoroughly wash linens and clothing that came into contact with ill family members

Medical Care

You might need to see your doctor if your symptoms last for longer than a few days. If your blood pressure is low or if you aren't urinating adequately, you might receive intravenous (IV) fluids to keep you hydrated.

If your infection is not improving on its own, you may need treatment with antibiotics or antiparasitic medication.

A Word From Verywell

The stomach flu is hard to avoid. Be sure to take care of yourself and to avoid spreading your infection to others when you get the stomach flu. Fortunately, these infections are typically short-lived and you should be back to yourself again within a few days. 

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