By Angela Ryan Lee, MD
Medically reviewed by Rochelle Collins, DO
The stomach flu is an infection that causes gastrointestinal symptoms including nausea, vomiting, and diarrhea. The medical term for stomach flu is viral gastroenteritis, which means inflammation of the stomach and intestines. You can contract viral gastroenteritis from exposure to infected individuals or from food or water containing certain viruses.
Read on to learn more about stomach flu and its causes and treatment, including how to manage it at home and what kind of foods to eat.
How Do You Know You Have the Stomach Flu?
The stomach flu is a viral infection, it requires exposure to a pathogenic virus. Things that increase likelihood of exposure or illness from stomach flu include:1
Exposure to someone with similar symptoms
Working in a daycare, hospital, or nursing home
Living in crowded spaces, such as dormitory or camp settings
Eating certain potentially contaminated foods, such as oysters
Those with compromised immune systems
Common Symptoms
The stomach flu is common, and chances are you have experienced it before. While symptoms are uncomfortable, they generally improve in a few days. Common symptoms include:2
Nausea
Vomiting
Loss of appetite
Abdominal cramping or discomfort
Diarrhea, including loose or watery stools and increased stool frequency
Fever
Fatigue
COVID and Stomach Flu Symptoms
While COVID-19 typically causes respiratory symptoms, in some cases it can cause gastrointestinal symptoms with or without any respiratory complaints.3 If you have symptoms of the stomach flu and you've had COVID exposure or suspect you may have COVID, it's reasonable to take a COVID test.
Dehydration
Stomach flu can lead to dehydration due to losses of water in vomiting and diarrhea, and difficulty with keeping enough fluids down. Signs and symptoms of dehydration include:4
Excessive fatigue
Dry mouth and increased thirst
Lightheadedness
Headache
Sunken eyes
Decreased urination and dark urine color
Increased heart rate
Rapid breathing
Low blood pressure
Dehydration is serious, and even fatal if untreated, so it's important to take symptoms of dehydration seriously. This is particularly true of certain people at higher risk, such as older adults, pregnant women, children, and infants. Anyone with symptoms of dehydration who are unable to keep fluids down to rehydrate should seek urgent medical attention.
Stomach Flu vs Food Poisoning: What's the Difference?
There is an overlap between stomach flu and food poisoning, with some subtle differences. Stomach flu is a term used specifically for viral gastroenteritis, meaning a virus causes it. It can be spread through contaminated foods, so some forms of food poisoning technically cause viral gastroenteritis. However, viruses that cause stomach flu may also spread among people, not just through food. So not all stomach flu is caused by food poisoning. On the other hand, food poisoning happens through ingesting contaminated food; viruses, bacteria, or parasites may cause it.
Is Stomach Flu Contagious?
Stomach flu is caused by a virus and is contagious, meaning it can be passed from person to person. It's spread through close contact or exposure to an infected person's stool or vomit. It can also spread through contaminated water, food sources, or eating utensils.
Common causes of the stomach flu include:5
Norovirus
Rotavirus
Astrovirus
Adenovirus
Should People with the Stomach Flu Quarantine?
It's a good idea for people with stomach flu to stay home to rest and recover, and avoid contact with others until a day or two after their symptoms improve. However, even after symptoms improve, there is still a potential for continued contagiousness. Proper hygiene with careful attending to handwashing, particularly after using the bathroom and before and after handling food or eating is good practice to avoid spreading or contracting the stomach flu.
Do not prepare food for others until at least two days after symptoms have improved.6
How Long Does the Stomach Flu Last?
Stomach flu usually improves within a few days, but the exact duration depends on the underlying pathogen. Symptoms may last as little as one day in the case of norovirus, or as long as one to twoweeks in the case of adenovirus.5
Treating the Stomach Flu at Home
Fortunately, most cases of stomach flu can be managed at home and do not require hospitalization or urgent medical care. There are some important steps to take for recovery, including staying well hydrated, getting rest, and slowly introducing food when you are able to.
What to Eat with Stomach Flu
Staying hydrated is of utmost importance with the stomach flu, so taking small sips of soup broth or an electrolyte solution, such as Pedialyte can be helpful.7 Ice chips can also help with rehydration when sips of water are not palatable. While fruit juices and energy drinks can provide both fluid and electrolytes, watch for sugar content since drinking sugary beverages can worsen dehydration.
With the stomach flu, there is inflammation of the stomach and intestines. This makes them more sensitive to certain foods, which can worsen symptoms. Once you are tolerating small sips of liquids, you can start introducing bland foods. While it is not evidence-based and should not be followed for a prolonged period, the BRAT diet has been historically recommended as a common sense, temporary way to start incorporating solids in the diet after gastroenteritis.8 The BRAT diet stands for:
Bananas
Rice
Applesauce
Toast
Other bland foods like saltine crackers, noodles or plain pasta, and lean meat like chicken may also be easy on the stomach as you start to incorporate foods back into the diet.
Foods to avoid during recovery include caffeine, spicy foods, dairy, and foods with high fat content, as these can worsen symptoms.9
Special Precautions: Severe Stomach Flu
Certain people may be more prone to getting stomach flu, or more likely to experience complications.
In Children
Children and infants are at higher risk of stomach flu due to exposure in daycare or school, and diapering/toileting, and weaker immune systems (in infants). They may also become dehydrated relatively quickly and can show different signs of dehydration. Reasons to call a pediatrician include:2
Any fever in an infant or high fever in a child
Diarrhea for more than one day in a child
Bloody stool
Severe abdominal pain
Concerning symptoms for dehydration such as lack of energy, irritability, less urination or decrease in the amount of wet diapers, lack of tears
In Older Adults
Older adults, particularly those with other underlying medical conditions, are at a higher risk of complications from stomach flu.2 They should be monitored carefully for symptoms of dehydration, especially confusion, which is a more common symptom in this age group.
When to See a Healthcare Provider
While most cases of stomach flu do not require specific medical care beyond supportive care at home, it's good to know when to seek medical attention. Look out for symptoms of dehydration, particularly severe dehydration, such as rapid heart rate, rapid breathing, low blood pressure, and confusion. These may indicate severe dehydration and should prompt immediate medical attention. In addition, see a healthcare provider for any signs of dehydration, especially in cases where a person cannot keep down liquids down due to frequent vomiting.
Other symptoms like high fever, bloody diarrhea, or persistent symptoms that do not seem to improve are reasons to seek medical attention.10
Summary
The stomach flu is an unpleasant experience marked by gastrointestinal symptoms. It's caused by viruses that cause inflammation of the stomach and intestines. Fortunately, it usually resolves within a few days, but it's important to stay hydrated. Seek medical attention for any concerning symptoms of dehydration and pay careful attention to infants, children, and older adults who may be affected.
Sources
Centers for Disease Control and Prevention. Viral agents of gastroenteritis public health importance and outbreak management.
MedlinePlus. Gastroenteritis (stomach flu).
Groff A, Kavanaugh M, Ramgobin D, et al. Gastrointestinal manifestations of COVID-19: A review of what we know. Ochsner J. 2021;21(2):177-180. doi:10.31486/toj.20.0086
MedlinePlus. Dehydration.
National Institute of Diabetes and Digestive and Kidney Diseases: Symptoms and causes of viral gastroenteritis ("stomach flu").
Centers for Disease Control and Prevention. Norovirus.
National Institute for Diabetes and Digestive and Kidney Diseases. Treatment of viral gastroenteritis ("stomach flu").
Centers for Disease Control and Prevention. Managing acute gastroenteritis among children.
National Institute for Diabetes and Digestive and Kidney Diseases. Eating, diet, & nutrition for viral gastroenteritis ("stomach flu").
Centers for Disease Control and Prevention. Food poisoning symptoms.
By Angela Ryan Lee, MD
Angela Ryan Lee, MD, is board-certified in cardiovascular diseases and internal medicine. She is a fellow of the American College of Cardiology and holds board certifications from the American Society of Nuclear Cardiology and the National Board of Echocardiography. She completed undergraduate studies at the University of Virginia with a B.S. in Biology, medical school at Jefferson Medical College, and internal medicine residency and cardiovascular diseases fellowship at the George Washington University Hospital. Her professional interests include preventive cardiology, medical journalism, and health policy.
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