Gastroenteritis (Stomach Flu) 101: Symptoms, Causes, Remedies & Treatment

How is stomach flu spread? How long does stomach flu last? Learn all about viral gastroenteritis (gastric flu or stomach flu) and its symptoms, causes, treatment and remedies.

by Alicia Teng

Gastroenteritis — or stomach flu — is a common digestive illness that affects both children and adults alike.

What is Stomach Flu (Gastroenteritis)?

Gastroenteritis is the inflammation of the gastrointestinal tract, which comprises the stomach and intestines. 

Calling gastroenteritis “stomach flu” is a bit of a misnomer — this inflammation can affect both small and large intestines alongside the stomach lining, and is also not caused by influenza viruses. Gastroenteritis is usually caused by viruses, though bacteria and parasites may occasionally be the cause.

A bout of gastroenteritis usually results in abdominal pain, vomiting, weakness and discomfort. This illness usually happens suddenly and is typically short-lived and most people recover fully with no long-lasting consequences. 

Stomach Flu Causes

Stomach flu is most commonly caused by viruses, though it can also be caused by bacteria, parasites and fungal infections. 

Here are the most common viruses that cause viral stomach flu:


The most common cause of viral gastroenteritis. Very contagious and commonly causes stomach flu outbreaks amongst people of all ages. Symptoms usually begin 12 to 48 hours after contact with the virus, lasting 1 to 3 days.


Commonly affects young children and is the leading cause of stomach flu outbreaks amongst that age group, though it can also infect adults. Symptoms usually begin about 2 days after contact with the virus and last for 3 to 8 days.
It’s recommended that you get your child vaccinated from the rotavirus when they are around 2 months old, to protect them from this virus. 

Bacterial gastroenteritis, on the other hand, is inflammation caused by bacteria rather than viruses. Common culprits of bacterial gastroenteritis include E. coli and salmonella, which is commonly spread through improperly handled or prepared food (see Food Poisoning). 

Though less common, it’s important to properly treat this type of stomach flu. 

Stomach Flu Symptoms

Common stomach flu symptoms include: 

  • Diarrhea
  • Nausea
  • Vomiting
  • Abdominal pain and cramps
  • Fever

High fever and bloody diarrhea are more commonly seen symptoms with bacterial gastroenteritis. 

Always consult a doctor if symptoms are severe or last for several days without improvement, as these may lead to complications.


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Stomach Flu vs Food Poisoning

The main differences between stomach flu and food poisoning is how the illness is caused. 

Stomach flu is usually caused by viruses and is usually contracted from direct contact with someone else who is sick. 

On the other hand, food poisoning develops when infectious organisms (usually bacteria, and occasionally viruses and parasites) contaminate foods and end up causing inflammation in the digestive tract. 

The most common way that one gets food poisoning is from eating contaminated or undercooked meat and seafood. 

Other foods that are more likely to cause food poisoning include:

  • Raw or undercooked eggs
  • Soft or unpasteurized cheeses
  • Vegetables and fruits that aren’t washed properly
  • Raw fish or oysters
  • Contaminated water
  • Unpasteurized beverages, such as milk, cider, and juice

Compared to stomach flu, symptoms of food poisoning may be more severe and may last for a shorter time. 

See How To Prevent Stomach Flu below for tips on how to keep you and your loved ones safe from both food poisoning and stomach flu.

How Long Does Stomach Flu Last?

Stomach flu typically happens suddenly and shortly after exposure, and usually lasts for a day to under a week. Most people affected by stomach flu tend to be able to recover without medical treatment and proper rest. 

However, if the symptoms of stomach flu last for over a week and symptoms are severe, the patient might develop dehydration that could lead to complications (see Stomach Flu Complications).

If a bout of stomach flu lasts unusually long, consult a doctor as soon as you can. 

Is Stomach Flu Contagious?

Viral stomach flu is highly contagious. 

It typically spreads through contact with an infected person’s stool or vomit — which occurs if the infected person doesn’t wash their hands thoroughly after using the bathroom and goes about their daily life. The virus can be spread through contact with surfaces, consuming food and drinks prepared by the infected person or direct contact with the infected person. 

Stomach Flu in Children

Due to its highly contagious nature and since children are especially susceptible to viral stomach flu, outbreaks at schools and childcare centres are common. There have been several cases of stomach flu outbreaks in Singapore that have made the news. 

Rotaviruses are usually responsible for stomach flu in children and infants, with most children experiencing at least one bout of stomach flu before they turn five. It is recommended that you get your child vaccinated from the rotavirus when they are around the age of two. 

Infants and children are also more at risk for complications from severe stomach flu. Persistent diarrhea and vomiting is especially dangerous in infants and young children as it can lead to dehydration in just a few days.

If your child has signs of stomach flu, do consult a doctor if their symptoms are concerning. 

Stomach Flu Complications

As mentioned previously, most cases of stomach flu are mild and while it causes discomfort, stomach flu usually resolves itself within a few days of rest.

Dehydration is the most likely complication of stomach flu. If symptoms like diarrhea and vomiting are persistent and last for more than a few days, your body loses fluids and electrolytes that are vital for its proper functions. 

Symptoms of dehydration may include: 

  • Feeling extreme thirst 
  • Fatigue
  • Dark-colored urine with less volume than usual
  • Sunken eyes or cheeks
  • Light-headedness or fainting

Dehydration from stomach flu is especially dangerous for children, the elderly, and immunocompromised individuals. If left untreated, dehydration can lead to organ damage, shock, coma, and even death.

Even though stomach flu usually goes away on its own, you should see a doctor as soon as possible if you experience: 

  • A change in mental state, such as irritability or lack of energy
  • Severe diarrhea that last more than 2 days
  • High fever 
  • Persistent vomiting and the inability to keep down any fluids
  • severe pain in the abdomen or rectum
  • stools that look black and/or contain blood

Stomach Flu Diagnosis

For mild cases of stomach flu, doctors usually provide a diagnosis based on your symptoms and a physical exam, without the need for further testing. 

Doctors may conduct a stool test if they deem necessary, in order to determine if the cause of the stomach flu is viral, bacterial or parasitic.

how to treat stomach flu

In most cases, people with viral gastroenteritis get better on their own without medical treatment. 

As dehydration is the most common complication, it’s important to combat it by drinking plenty of fluids. You may also drink electrolyte-rich sports drinks or consume saltine crackers to  replace the lost electrolytes. 

Your doctor may prescribe you with antidiarrheal and anti-nausea medicines to mitigate stomach flu symptoms. Over-the-counter medications that may also help relieve symptoms include loperamide hydrochloride (Imodium) and bismuth subsalicylate (Pepto-Bismol). 

If you feel too weak to make your way to the clinic, you can choose to consult a doctor online and have stomach flu medicine delivered to your doorstep.

Over-the-counter medications may be unsafe for infants and children to take. Always consult your doctor or pediatrician before administering medication to your child. 

Best Food for Stomach Flu: What to Eat And What to Avoid

Most medical experts don’t recommend fasting or restricting your diet too much when you’re recovering from stomach flu. 

Since it can be hard to eat when you’re feeling nauseous, choose bland, easy-to-digest foods to start with and consume them in small quantities. 

Some good food choices include:

  • Bananas
  • Lightly seasoned porridge 
  • Oatmeal
  • Saltine crackers
  • Toast
  • Potatoes 
  • Fresh fruit
  • Broths 
  • Poached or baked meats (chicken, white fish and other lean proteins)

Certain foods might make symptoms such as nausea and diarrhea worse. Some foods to avoid while you’re recovering from stomach flu include:

  • Caffeinated drinks such as coffee, tea, and energy drinks
  • Fried food, pizza, burgers and other fatty, heavily-seasoned foods
  • Candy, donuts, cookies, soft drinks and any other food that is high in sugar
  • Dairy products that contain lactose, such as ice-cream and milk
  • Spicy foods

How to Prevent Stomach Flu

Prevention is better than cure. Since stomach flu is so contagious, it is important to ensure that you and your loved ones are protected from a potential stomach flu outbreak.

Always wash your hands thoroughly with antibacterial soap and water after using the bathroom, changing diapers, as well as before and after handling, preparing and eating food. 

When preparing food, always:

  • Wash your hands after touching raw meat or seafood
  • Avoid keeping uncovered raw meat and half-eaten food in the refrigerator
  • Avoid eating uncooked eggs

Note that, even as simple as washing your hands and preparing your food thoroughly can help you avoid any health-related issues. Proper hygiene and being thorough in everything you do certainly can go a long way.

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  2. Viral Gastroenteritis. National Institute of Diabetes and Digestive and Kidney Health. Retrieved 3 June 2021, from 
  3. An Overview of the 24-Hour Stomach Flu VeryWell Health. Retrieved 3 June 2021, from 
  4. Is It a Stomach Bug or Food Poisoning? Healthline. Retrieved 3 June 2021, from 
  5. Gastroenteritis. NHS Inform. Retrieved 3 June 2021, from 
  6. Signs of Stomach Flu and When to See a Doctor. VeryWell Health. Retrieved 3 June 2021, from
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About the Writer
Alicia Teng
Alicia is a founder of boutique gym Division Athletics. When she's not coaching classes or sweating it out on the gym floor, she freelances as a food and lifestyle writer. Alicia is also addicted to kueh.
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