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What exactly is stomach flu? A bewildering variety of digestive system problems are all called “stomach flu” or “stomach bug”—intestinal infections, parasites, food allergies, food poisoning. However, when it comes to stomach flu outbreaks, the offender is mostly commonly a virus, referred to as viral gastroenteritis.
What is the stomach flu?
Viral gastroenteritis (“stomach flu” or “stomach bug”) is a viral infection of the stomach and intestines that causes diarrhea, nausea, vomiting, stomach pain, and abdominal cramping. While most cases resolve in a few days without serious problems, viral gastroenteritis can be a serious and even life-threatening infection in very young children, seniors, or people with immune system problems.
Several different viruses can cause stomach flu, but nine in ten cases are caused by norovirus. Rotavirus is usually the culprit when young children come down with stomach flu, but rotavirus vaccines have drastically reduced the incidence in the United States. Other viruses such as adenovirus (the cold virus), astrovirus, and sapovirus are responsible for a small number of cases, chiefly among infants and children. The influenza virus, however, never causes stomach flu, so a flu shot does not help prevent stomach flu.
Bacteria can also cause gastroenteritis, most commonly Shigella, Salmonella, Campylobacter, and E. coli. Treatment and medications for bacterial gastroenteritis are covered more fully in their own articles.
Viral gastroenteritis often occurs in outbreaks. Closed communities such as long-term care facilities, daycare centers, schools, prisons, and cruise ships are particularly vulnerable to outbreaks. Gastroenteritis viruses spread from person-to-person primarily through what is called the fecal-oral route. This occurs when microscopic fecal contaminants are incidentally ingested. Contaminated food is the most common cause of infection, particularly food that is served raw, washed in contaminated water, or handled after being cooked. However, people can pick up infected fecal material from person-to-person contact, clothes, furniture, utensils, or even floating in the air.
Norovirus is a particularly contagious, tough, and long-lasting virus. It can survive extreme heat, freezing cold, withstand many disinfectants, and survive on surfaces for up to two weeks. For this reason, norovirus is responsible for over half of all foodborne outbreaks. About 21 million people in the United States get sick and nearly 800 people die from norovirus infection each year.
An additional 3 million cases of viral gastroenteritis—almost all infants or very young children—are caused by rotavirus. Most adults and older children, however, are immune to rotavirus. Anyone can catch stomach flu, but infants, young children, seniors, and people with compromised immune systems are at a higher risk for infection. Other risk factors include eating out frequently, attending a daycare center or school, living in a nursing home, or staying in cruise ships, hotels, or other partly-closed communities. Poor hand washing habits also increase the likelihood of a gastrointestinal viral infection.
Most cases of viral gastroenteritis typically resolve in a few days. Treatment consists mainly of supportive care. Dehydration is the most serious complication, so supportive care mainly focuses on maintaining sufficient hydration. Medications can help with nausea, vomiting, or diarrhea. However, infants, the elderly, and people with compromised immune systems may require hospitalization.
How is the stomach flu diagnosed?
Stomach flu is primarily diagnosed through a physical examination and a patient medical history. Most cases will be diagnosed and treated by a general practitioner.
Symptoms are the best guide for diagnosis. The defining symptom of stomach flu is loose or watery diarrhea, but other symptoms might include.
- Nausea
- Vomiting
- Abdominal pain
- Low-grade fever
Loss of appetite, involuntary weight loss, and bloating might also be experienced.
Symptoms of gastroenteritis usually start suddenly (or ‘acutely’, hence the term ‘acute gastroenteritis’), coming on in one or two hours. In addition to how quickly symptoms started, a healthcare provider will want to know:
- How long have you had symptoms?
- Do other people you know have similar complaints?
- Did you eat anything unusual recently, such as raw foods?
- Did you travel recently, especially outside the country?
A physical examination will help the healthcare professional rule out other conditions. The healthcare provider will carefully look for signs of dehydration, such as sunken eyes, limpness, dry mucous membranes (inside the mouth), loose skin, or drowsiness.
Blood or stool tests are not necessary to diagnose a viral gastroenteritis, but a healthcare provider will use them to rule out other causes, such as a bacterial infection, parasite infection, or other intestinal problems. Blood or urine tests may be necessary if there are signs of dehydration.
Stomach flu treatment options
Most cases of viral gastroenteritis resolve on their own, typically in one to three days, depending on the virus. Treatment of viral gastroenteritis focuses entirely on managing symptoms, particularly dehydration. Bacterial gastroenteritis, the subject of other articles, is treated with both antibiotics and symptom support.
Supportive care
The primary focus of supportive care is to maintain hydration and electrolytes. Drinking fluids or using over-the-counter oral rehydration solutions (ie, Pedialyte, Gatorade, Powerade) are the principal treatments. IV fluids and hospitalization may be required for more severe dehydration.
Medications
Over-the-counter or prescription medications can provide symptom relief for nausea, vomiting, or diarrhea. Antibiotics fight bacteria (not viruses), so while they are effective against bacterial gastroenteritis, they are not effective against the viruses that cause stomach flu.
Stomach flu medicine
Viral gastroenteritis typically resolves in a few days without medical intervention. Over-the-counter medications can help manage stomach flu symptoms such as dehydration, nausea, vomiting, and diarrhea. Severe cases, though, may require more powerful prescription medications to prevent serious dehydration.
Oral rehydration solutions
Oral rehydration solutions such as Pedialyte, Hydralite, or Ensure Rapid Hydration, replace fluids and electrolytes lost to vomiting or diarrhea. The electrolytes in many commercially-available oral rehydration solutions are balanced to ensure the most effective fluid absorption. While commercially-available oral rehydration solutions are better than sports drinks, a combination of ice and water is usually sufficient for handling mild gastroenteritis.
Antiemetics
Antiemetics (anti-nausea medications agents) reduce nausea and vomiting by slowing down the part of the brain responsible for nausea and the vomiting reflex. For mild gastroenteritis, over-the-counter antiemetics such as dimenhydrinate or meclizine are usually sufficient to keep nausea and vomiting in check. If severe dehydration is a problem, a doctor or emergency room physician may use a more potent prescription antiemetic such as ondansetron, metoclopramide (reduces nausea and vomiting by making the stomach contract), or prochlorperazine. These drugs may initially be administered intravenously.
Antidiarrheal agents
As a general rule, people with mild gastroenteritis who can stay hydrated shouldn’t take antidiarrheal drugs. If dehydration or severe diarrhea is an issue, however, over-the-counter antidiarrheal agents can help. Antimotility agents such as loperamide, work by slowing down the colon. Bismuth salts (bismuth subsalicylate) coat the intestinal tissues and prevent water and electrolytes from being secreted into the stools. Both types of drugs let fecal material build up in stools before being passed.
What is the best medication for the stomach flu?
Medications only treat stomach flu symptoms, but most people can endure a bout of stomach flu without medications. There is, then, no “best” medication for stomach flu, only a combination of drugs that decreases the risk of complications, reduces discomfort, and has a minimum of unpleasant side effects.
| Best medications for stomach flu | ||||
|---|---|---|---|---|
| Drug Name | Drug Class | Administration Route | Standard Dosage | Common Side Effects |
| Pedialyte | Oral rehydration solution | Oral | Small frequent sips every 15 minutes to a daily total of one to two liters | Nausea, vomiting, diarrhea |
| Dramamine (dimenhydrinate) | Antiemetic | Oral | Dose depends on age. Taken every four to six hours (adults) or every six to eight hours (children) | Drowsiness, dizziness, dry mouth |
| Travel Sickness Antivert (meclizine) | Antiemetic | Oral | Two to four 12.5 mg caplets once daily | Drowsiness, dry mouth, headache |
| Zofran (ondansetron) | Antiemetic | Oral | One or two 4 mg tablets every six hours | Headache, drowsiness, lightheadedness |
| Reglan (metoclopramide) | Antiemetic | Oral | One 10 mg tablet taken 30 minutes before each meal and at bedtime for two to eight weeks | Restlessness, drowsiness, fatigue |
| Compazine (prochlorperazine) | Antipsychotic (antiemetic) | Oral or rectal | One 5 mg or 10 mg tablet three to four times daily | Restlessness, blurred vision, dry mouth |
| Pepto-Bismol (bismuth subsalicylate) | Antidiarrheal agent | Oral | Two tablets every half hour or four tablets every hour as needed | Constipation, abdominal pain, black tongue and stool |
| Imodium A-D (loperamide) | Antidiarrheal agent | Oral | Two 2 mg capsules followed by one 2 mg capsule after each unformed stool | Constipation, dry mouth, flatulence |
Many of the standard dosages above are from the U.S. Food and Drug Administration (FDA) and the National Institutes of Health (NIH). Dosage is determined by your doctor based on your medical condition, response to treatment, age, and weight. Other possible side effects exist. This is not a complete list.
What are the common side effects of stomach flu medicine?
Stomach flu medications will vary in their side effects based on the type of drug, the dose, and the patient’s age. This is not a complete list of side effects, so consult with a health care provider about possible drug interactions or side effects.
Oral rehydration solutions have a long track record of safety. Rare side effects include nausea and diarrhea. It is possible, however, to overdo it. Taking too many electrolytes can throw the body’s balance of electrolytes off-kilter, causing potentially serious medical problems.
Antiemetics work by affecting a part of the brain involved with nausea and vomiting, so drowsiness, lightheadedness, sleepiness, restlessness, and agitation are the most common side effects. Dry mouth is a common complaint. The most serious side effect involves a hazardous change in the way the heart beats called QT prolongation. The risk is greatest when these drugs are taken over a long period.
The most commonly experienced side effect of antidiarrheal agents is constipation. Abdominal pain, nausea, and vomiting are also possible.
Bismuth subsalicylate, better known as Pepto-Bismol, contains an ingredient that is closely related to aspirin, so it should not be taken by people with allergies to aspirin, bleeding problems, stomach ulcers, or gastritis. Like aspirin, bismuth subsalicylate can cause Reye’s syndrome, a condition that can cause serious and even fatal liver and brain damage in children. It should never be given to children or teens with viral gastroenteritis, fever, or any kind of viral infection.
What is the best home remedy for stomach flu?
There isn’t much that medication can do for viral gastroenteritis other than relieve symptoms. Most people, then, just push through a bout of stomach flu with bed rest and a few tried and true home remedies.
Drink fluids
When battling the stomach flu, your number one priority is staying hydrated. Plain water, however, is not the best choice. Instead, drink diluted apple juice or oral rehydration solutions throughout the day. Children should be served a cup of diluted apple juice followed by their preferred drink. Take small sips rather than big gulps to make sure the fluids stay down.
Replenish electrolytes
Besides dehydration, diarrhea can cause a significant loss of electrolytes, throwing the body’s electrolytes off-balance. Make sure you consume electrolyte-rich foods such as broths, soups, and bananas. Over-the-counter oral rehydration solutions are also an excellent source of electrolytes.
Eat small meals
To prevent nausea and vomiting, eat a few small meals throughout the day rather than two or three big meals. Bland and mushy foods are best: bananas, applesauce, bread, soda crackers, gelatin, and broth. The BRAT diet (bananas, rice, applesauce, and toast) is an old, familiar home remedy for an upset stomach, but there are no strong studies to support its use.
Avoid irritating foods and drinks
Spicy foods, dairy products, fatty foods, carbonated drinks, coffee, and alcohol may provoke nausea and vomiting and diarrhea.
Avoid certain medications
When infected with a stomach virus, avoid nonsteroidal anti-inflammatory drugs (NSAIDs) such as aspirin or ibuprofen. These drugs can worsen stomach irritation, making nausea, vomiting, and stomach pain worse. If you must take a pain reliever, use acetaminophen until your health improves.
Rest
Fighting intestinal viruses is a bit of a workout, so give the body plenty of bed rest.
Practice good hygiene
While someone fights off the stomach flu, the body is shedding trillions of viral particles in the feces. In fact, in a person infected with norovirus, just one gram of feces contains enough virus to infect five billion people. A big part of treating stomach flu, then, is keeping other people safe:
- The infected person should wash hands regularly throughout the day. Hand sanitizer is not 100% effective for some viruses.
- No infected person should prepare or touch other people’s food, dishes, napkins, or eating utensils.
- The infected person should use a separate bathroom.
- No infected person should share towels, clothes, or bedclothes.
- Disinfect hard surfaces with bleach or hydrogen peroxide.
Frequently asked questions about stomach flu
How do you get rid of the stomach flu fast?
Viral gastroenteritis typically clears in one to a few days depending on the virus. There’s little to be done other than alleviating symptoms with home stomach flu remedies and over-the-counter medications.
How long does the stomach flu last?
Most cases of viral gastroenteritis resolve on their own. A norovirus infection typically lasts one to three days, but rotavirus gastroenteritis can take up to a week to clear. Viral gastroenteritis caused by adenovirus or astrovirus holds on longer, typically taking five to 12 days to resolve. Gastroenteritis that lasts longer than two weeks, or chronic gastroenteritis, is usually due to a bacterial or parasite infection.
Does the stomach flu go away on its own?
Nearly all cases of viral gastroenteritis clear up on their own in a few days. Treatment focuses almost entirely on controlling symptoms and complications. The most serious and potentially life-threatening complication is dehydration, so maintaining proper hydration is the number one concern.
Related resources for stomach flu
- Gastroenteritis in children. American Family Physician
- Nausea and vomiting: Care and treatment. Cleveland Clinic
- Norovirus. Centers for Disease Control and Prevention (CDC).
- Rotavirus. Centers for Disease Control and Prevention (CDC)
- The importance of staying hydrated. Harvard Health
- Viral Gastroenteritis. StatPearls