By Mark Gurarie 

 Medically reviewed by Suzanne Fisher, RD

If you’ve ever had the stomach flu, known as gastroenteritis, you’re far from alone. Infection with norovirus, the most common cause, is the second most common illness in the US.1 Occurring due to infection and inflammation of the intestines and stomach, typical symptoms include fever, diarrhea, abdominal pain, and vomiting.

In most cases, stomach flu resolves without medical management, and there’s no outright cure for it. Ensuring you get rest, staying hydrated, and making dietary changes are among the strategies to help you manage stomach flu.2 It’s important to understand the symptoms and causes of this common condition as well as what home remedies and medical approaches look like.

What Is Stomach Flu?

Stomach flu symptoms arise due to an inflammation of the tissues of your intestines and stomach (parts of the gastrointestinal tract). It arises due to infection, most often with the norovirus,a type of viral gastroenteritis. Despite being called "stomach flu," it’s not actually caused by the influenza (flu) virus virus; however, both diseases can be very contagious. As an acute condition, this illness that causes diarrhea generally affects you for a short time and resolves within a week.1

At-Risk Groups

Gastroenteritis tends not to be severe in healthy adults, though it can be fatal in infants, people over age 65, and those with weakened immune systems.2 People who are immunocompromised (have weakened immune systems) include those who have existing health conditions, are taking certain medications that lower their immunity, or undergoing chemotherapy.

Symptoms

The most common symptoms of gastroenteritis are:1

• Watery diarrhea

• Cramping and pain in the abdomen

• Vomiting and nausea

• Fever, in some cases

The most significant complication of stomach flu is dehydration as this can become dangerous, or even fatal. In adults, this can cause an array of additional signs, including:1

• Dry mouth and thirst

• Less urine than normal

• Dark-colored urine

• Loss of energy, fatigue

• Sagging eyes and cheeks

• Dizziness

• No tears when crying

• Reduced skin elasticity, or turgor (skin not returning into position after a pinch)

Parents of infants should also recognize the signs their child is dehydrated. These include:1

• Less urine in their diapers

• Extra thirst

• Loss of energy

• Lack of tears

• Sunken cheeks or eyes

• Fussiness and restlessness

Causes of the Stomach Flu

Fundamentally, stomach flu symptoms are the result of inflammation in the gastrointestinal system. This can be caused by viruses (viral gastroenteritis), bacteria, parasites, or chemicals.1

Viral Gastroenteritis

Viral forms of stomach flu are highly contagious as the virus spreads through contact with an infected person’s stool or vomit. It can be picked up from direct contact with that person, contaminated food, or after touching a surface and then your mouth without washing your hands.

Most gastroenteritis cases are caused by three viruses, which are:

• Norovirus: By far the most common form of stomach flu is norovirus infection, which causes inflammation of the stomach and intestines. Symptoms set on within 24 to 48 hours of exposure and usually resolve within 24 to 72 hours.3 It can affect people of all ages.

• Rotavirus: Primarily affecting infants and children under age 5 (though adults also catch milder forms), rotavirus causes vomiting and diarrhea for three to eight days.4 This type of gastroenteritis is vaccine-preventable.           

• Adenovirus: The highly contagious adenovirus causes mild cold and flu symptoms three days after infection; they last up to two weeks.1 Most at risk are people with weaker immune systems, such as younger children and infants, older people, and those with existing conditions

• Astrovirus: As with some others, being older, a child or infant, or having compromised immunity makes you more likely to become infected with astrovirus. Stomach flu due to astrovirus arises four to five days after infection, resolving within one to four days.5

Seasonal Outbreaks

In the United States, most viral gastroenteritis outbreaks are due to norovirus, rotavirus, and astrovirus and occur during the winter months.1 This is because most spend more time indoors and in close quarters to others when it’s colder, increasing the chances of transmission.  

Bacterial Gastroenteritis

Certain bacterial infections can also cause stomach flu, though this type of gastroenteritis is rarer than viral types. The bacteria causing food poisoning grow on foods like meat, fruits, and vegetables, as well as other food; water and liquids can also be contaminated. Primarily, three types of bacteria cause bacterial gastroenteritis:6

• E. coli

• Salmonella

• Campylobacter

Parasites and Contaminants

Gastroenteritis may also arise due to infection with microorganisms, as in giardiasis. This is an infection of the Giardia duodenalis parasite, often referred to as giardia. Following contact, these microbes reside in the intestines and pass through the feces.7

Another parasite that causes gastroenteritis is Cryptosporidium, infections that lead to cryptosporidiosis, commonly known as crypto. Like giardia, this parasite survives in the intestines and spreads via contact with human or animal feces.8

Lastly, exposure to certain chemicals and contaminants can cause diarrhea, vomiting, and other gastroenteritis symptoms. As with the others, transmission is often through contaminated food or drink.

Food Poisoning

When what you eat or drink is contaminated with viruses, bacteria, contaminants, or parasites, you contract food poisoning. This is a type of gastroenteritis.   

Home Remedies for the Stomach Flu

In most cases, stomach flu resolves on its own, without the need for medications or medical treatments. Healing from the condition primarily means managing the symptoms, getting rest, staying hydrated, and boosting electrolyte intake.9 Treating gastroenteritis primarily involves dietary restrictions, drinking water, and getting rest.

There’s much you can do to prevent the infections that cause this condition.   

Diet

Since stomach flu causes nausea and vomiting, eating and getting enough nutrients can be challenging. Making dietary changes is a cornerstone of gastroenteritis treatment.10

The BRAT (bananas, rice, applesauce, and toast) diet is designed to ease the symptoms of stomach flu, diarrhea, and nausea. It consists of foods that are low in protein, fiber, and fat, which are easier to digest. These are foods that are bland and easy to chew. There is, however, limited evidence of its efficacy.10

It is recommended to choose soft, low residue/low fiber foods, unseasoned lean protein sources (poultry/eggs), tea, broth, and hydration fluid, such as Pedialyte, and avoiding dairy.

It is best to start with a liquid-based diet and work up to more solid foods.11

Recommended Foods

Bouillon or broth

Apple or cranberry juice

Popsicles (ice pops) and hard candies

Saltines or white bread

Toast, plain pasta, or rice

Bananas

Mashed potatoes

Lean protein (poultry/eggs)

Not Recommended Foods

Spicy or fried foods

Alcohol

Caffeinated beverages

Dried peas or beans

Raw or dried fruits and vegetables (bananas are recommended)

Whole grain cereals or breads

Milk and dairy products, like cheeses, butter, etc.

Seeds, nuts, popcorn, and coconut

Drink Water

The primary focus of treatment for gastroenteritis involves ensuring you don’t become dehydrated. Central to management is fluid and electrolyte intake. This may involve:1

• Drinking water

• Eating saltine crackers (a source of electrolytes)

• Drinking beverages with electrolytes, such as Gatorade or Pedialyte

• Drinking broth

Additionally, a provider may recommend oral rehydration therapy. This requires drinking a preformulated solution of water, bicarbonate, glucose, and sodium chloride (electrolytes) throughout the day.12

Rest

One of the most important things your body needs to fight off infection is plenty of rest. Take time off of work, keep your child out of school or daycare if they're infected, and make sure you and your child is getting enough sleep. This will help strengthen the immune system and allow you time to recoup.  

Prevention

Gastroenteritis is highly communicable; the viruses, bacteria, and other pathogens that cause it are often resilient and able to survive on surfaces or foods. Ways to prevent infection include:9

• Proper handwashing: Give your hands a thorough cleaning after going to the bathroom and changing diapers; make sure you’ve done so prior to and after handling any food.  

• Cleaning surfaces: If surfaces have come into contact with vomit or feces, they need to be fully cleaned and sanitized. Use a solution of 5 to 25 tablespoons of bleach to 1 gallon of hot water. Dirty clothing should be washed at the longest possible cycle with detergent.

• Washing food items: Contaminated foods can be vectors (transmitters) for infections that cause gastroenteritis. Make sure to thoroughly wash fruits and vegetables and cook meats, shellfish, and clams all the way through.

Safe Food Handling

If you’re sick, you can spread gastroenteritis by handling food. Make sure to very thoroughly wash your hands or put on rubber gloves before touching anything you’ll be eating.  

Medical Treatment

In some cases, home management of stomach flu isn’t enough to stop nausea, diarrhea, and other symptoms. You may be prescribed:12

• Antibiotics, such as Cipro (ciprofloxacin), may help in cases of bacterial gastroenteritis but not if it’s viral or due to a parasite.

• Imodium (loperamide), Pepto-Bismol (bismuth subsalicylate), or Lomotil (diphenoxylate) may help with loose stools and diarrhea.

• Daily probiotics, such as Lactobacillus, may also be recommended to aid digestion.

• Over-the-counter (OTC) oral rehydration solutions, such as Pedialyte

• Intravenous (IV) rehydration in cases of severe dehydration

• Rotavirus vaccine, administered to infants at two, four, and sometimes six months

Medicate With Care

If you’re taking prescribed or OTC medications for gastroenteritis, do so with care. Be mindful of your condition and use them only as directed. Let your healthcare provider know if you’re experiencing debilitating side effects or worsening symptoms.

When to Seek Medical Attention

Gastroenteritis symptoms can be especially dangerous for certain populations, prompting a call to your provider. These include:9

• Infants

• Children born prematurely

• Pregnant women

• People with a weakened immune system (due to illness, autoimmune conditions, etc.)

• People undergoing chemotherapy

• People over 65 years old  

In addition, if an infant is not drinking or has had diarrhea for two days, you should seek immediate medical attention.

Furthermore, the following symptoms warrant medical help:9

• Irritability, lack of energy, or altered mental state

• Diarrhea for more than two days

• High fever

• Frequent vomiting

• Six or more loose stools (bouts of watery diarrhea) in one day

• Severe pain in the abdomen or rectum (the lowermost part of the intestines)

• Blood and pus in the stool; stool with a black or tarry appearance

• Dehydration symptoms

Summary

Stomach flu, or gastroenteritis, is an inflammation of the intestines and stomach that causes diarrhea, vomiting, nausea, and sometimes fever. Symptoms typically resolve within two weeks—often within one to three days—without medical treatment.2 Gastroenteritis symptoms can cause severe dehydration.

While this condition is often viral in origin, with most cases arising due to norovirus infection, it can also be the result of exposure to bacteria, such as E. coli, parasites like giardia, or chemicals.3 Stomach flu can be highly contagious.1 Infants and children, older people, and those with compromised immunity are more likely to develop stomach flu.

The goals of treatment for gastroenteritis are to prevent dehydration, get rest, manage symptoms, and employ a restricted diet. This may involve drinking water or drinks with electrolytes, prioritizing sleep and rest throughout recovery, and taking OTC medications, such as Imodium (loperamide) and probiotics.9 Signs of dehydration prompt immediate medical attention.  

Sources

National Institutes of Health. Definition & facts for viral gastroenteritis (“stomach flu”). U.S. Department of Health and Human Services.

National Institutes of Health. Viral gastroenteritis (“stomach flu”). U.S. Department of Health and Human Services.

Centers for Disease Control and Prevention. About norovirus.

Centers for Disease Control and Prevention. Rotavirus clinical information.

Jeong HS, Jeong A, Cheon DS. Epidemiology of astrovirus infection in children. Korean J Pediatr. 2012;55(3):77–82. doi:10.3345/kjp.2012.55.3.77

Johns Hopkins Medicine. Bacterial gastroenteritis.

Centers for Disease Control and Prevention. Giardia: General information.

Centers for Disease Control and Prevention. Parasites: Cryptosporidium (also known as “Crypto”).

Centers for Disease Control and Prevention. Treatment of viral gastroenteritis (“stomach flu”).

Barr W, Smith A. Acute diarrhea in adults. Am Fam Physician. 2014;89(3):180-189.

Brown University Health Services. Viral gastroenteritis.

Graves N. Acute Gastroenteritis. Prim Care. 2013;40(3):727-741. doi:10.1016/j.pop.2013.05.006

Additional Reading

Centers for Disease Control and Prevention. Treatment of viral gastroenteritis (“stomach flu”).

National Institutes of Health. Definition & facts for viral gastroenteritis (“stomach flu”).

By Mark Gurarie
Mark Gurarie is a freelance writer, editor, and adjunct lecturer of writing composition at George Washington University