An Overview of the 24-Hour Stomach Flu

What You Should Know About Gastroenteritis

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A stomach bug is known for its symptoms of nausea, vomiting, and diarrhea, and you may have called it something like the "stomach flu." It's actually gastroenteritis, an inflammation commonly caused by an infection like norovirus.

Most cases are easily treatable, but stomach bugs are highly contagious. It's also unlikely that what you think of as a "24-hour bug" will always resolve that quickly, and when symptoms last longer than that you should call your healthcare provider.

This article discusses stomach bug causes, diagnosis, and treatment. It details why these illnesses are not the flu, along with some strategies to prevent them from happening in the first place.

African-american woman holds stomach - stock photo

Catherine McQueen / Getty Images

Stomach Bug Symptoms

A stomach bug is really an infectious diarrhea, so that's a main symptom of gastroenteritis. It's caused by the inflammation in your stomach and gastrointestinal tract (digestive system).

Gastroenteritis also leads to other symptoms that include:

  • Abdominal pain and cramps
  • Nausea
  • Vomiting
  • Fever
  • Chills
  • Headache

A stomach bug generally comes on suddenly and hits hard. The symptoms then gradually decrease as you get better.

Stomach Bug Causes

The stomach flu can be caused by a lot of things, including viruses, bacteria, and parasites.

Common Viral Causes

Stomach bugs are often caused by viruses. The typical culprits include:

  • Rotavirus: Most common in babies between 3 months and 15 months old
  • Adenovirus: Most common in children under 2
  • Norovirus: Most common cause of adult cases
  • Astrovirus: Affects all ages; typically known for mild infections in children, but researchers are finding strains that affect the nervous system and may lead to life-threatening complications.

Most Common Stomach Bug

About 60% of all stomach flu cases in the United States are due to norovirus. That comes out to around 21 million norovirus infections each year.

Viruses that cause stomach bugs are extremely contagious and easily passed from person to person.

The fecal-oral route (from not washing hands after defecating, changing diapers, digging in contaminated soil, etc.) is the primary mode of transmission, with the following also playing a role:

  • Direct contact with a sick person
  • Aerosolized (airborne) particles from vomit
  • Consuming contaminated food and water
  • Surfaces contaminated with norovirus

Symptoms may last for just a day or two, or they may continue for more than a week.

Common Bacterial Causes

Bacterial causes of stomach flu include:

Bacteria-associated gastroenteritis is primarily related to something you ate. Campylobacter strains account for around one-third of all bacterial cases.

Many of these infections are transmitted through contaminated poultry or other tainted foods, including meat, produce, and dairy products.

Symptoms may last for between one and 10 days.

Common Parasitic Causes

Stomach bugs are less commonly caused by parasites. The primary culprits are:

The parasites are spread through food, water, or soil that's contaminated with infected feces. These cases may last longer than is typical of viral or bacterial stomach flu, with symptoms lasting between two and six weeks.

Is a Stomach Bug Really the Flu?

When describing a stomach bug, "flu" is a misnomer. In medical terms, the flu (influenza) is a common viral respiratory infection. It involves symptoms such as:

When you get a flu vaccine, this is what you're being protected from—not gastroenteritis.

Stomach Flu
  • AKA gastroenteritis, infectious diarrhea

  • Gastrointestinal infection that can be caused by a virus, bacterium, or parasite

  • Spreads through person-to-person contact, contaminated food or water, or contact with infected feces

  • Symptoms include vomiting, diarrhea, fever, and stomach pain

  • Vomiting usually lasts 24 hours; diarrhea may continue for several days

  • Most can't be prevented with a vaccine

  • AKA seasonal influenza

  • Upper respiratory infection caused by a virus

  • Spreads through droplets in the air caused by coughing or sneezing

  • Symptoms include fever, chills, muscle aches, cough, and congestion

  • May last from two to 10 days

  • May be prevented with a yearly vaccine

Diagnosing Stomach Bugs

You may know the cause of your stomach flu before even seeing a healthcare provider, especially if, for example, you and several others get sick after eating at a restaurant. If symptoms aren't severe and only last a few days, you likely won't need medical attention.

If you do see a healthcare provider, they may diagnose gastroenteritis just from the symptoms and circumstances you describe. They'll also likely be aware of anything that's spreading through the community.

In severe or prolonged cases, your provider may need more information. They may order:

Those tests should reveal whether the cause is viral, bacterial, or parasitic, which can guide treatment recommendations.

Is It COVID-19?

Sometimes COVID-19 can cause gastroenteritis-like symptoms. In some people, these symptoms may be present even if respiratory symptoms aren't.

Treating Stomach Bugs

Stomach bug symptoms usually go away on their own. The main focus of treatment is to prevent dehydration due to fever, vomiting, and diarrhea.

how to treat the stomach flu

​Verywell / Emily Roberts

Supportive therapies may include:

  • Rehydration with water or electrolyte-rich sports drinks (avoid sugary sodas and fruit juice)
  • A BRAT diet (banana, rice, apple, and toast) to ease a queasy stomach and stop diarrhea
  • Anti-nausea medicines like Reglan (metoclopramide) or Zofran (ondansetron) to reduce vomiting and lessen the risk of dehydration
  • Anti-diarrheal medication like Pepto-Bismol (bismuth subsalicylate) or Imodium (loperamide); don't use these in children or if you have bloody stools
  • Tylenol (acetaminophen) to relieve fever; other over-the-counter fever reducers (ibuprofen, naproxen, aspirin) are more likely to upset your stomach

Antibiotics can be prescribed to help clear up a bacterial or parasitic infection that's caused the gastroenteritis. However, they're ineffective against viruses that commonly cause infection.

Stomach Bug Prevention

You're better off preventing gastroenteritis than treating it. Frequent hand washing, especially after using the toilet, and good food hygiene help to prevent the transmission of stomach flu.

When to Call a Healthcare Provider

If you are pregnant, immunocompromised, over age 65, or recently hospitalized or on antibiotics, you should contact your healthcare provider for advice.

Call your healthcare provider immediately or go to the emergency room if you have:

  • Vomiting for more than 24 hours
  • Diarrhea for several days
  • Violent vomiting
  • Blood in your vomit or stool
  • Trouble keeping fluids down
  • Signs of severe dehydration (no urine for more than eight hours, dizziness, weakness, confusion, fainting, fever over 101 degrees F)


A stomach bug is spread by contaminated food or water. It's also transmitted through person-to-person contact. It is not the same as the flu (influenza).

Common symptoms of the stomach bug include fever, abdominal distress, nausea, vomiting, and diarrhea. Sometimes, stomach flu may go away after 24 hours. But it may take up to 10 days before you fully recover.

Treatments may involve antibiotics, medications to stop vomiting and diarrhea, and good hydration. Get medical help for severe symptoms.

Frequently Asked Questions

  • How long does gastroenteritis last?

    Despite the nickname "24-hour stomach flu," most cases of gastroenteritis last longer than a day. Depending on the cause, stomach flu can linger for up to 10 days.

  • What happens inside your body when you have a stomach bug?

    In most cases, viruses, bacteria, or other microbes invade your intestine, producing toxins that cause vomiting, diarrhea, inflammation, and other symptoms.

  • Do crackers help stomach flu?

    Yes, eating saltine crackers can help to prevent dehydration and maintain electrolytes in your body.Mashed potatoes, bananas, and broths are other foods that may help with symptoms.

20 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Kristina Duda, RN
Kristina Duda, BSN, RN, CPN, has been working in healthcare since 2002. She specializes in pediatrics and disease and infection prevention.