A Overview of the 24-Hour Stomach Flu

What You Should Know About Gastroenteritis

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If you've suddenly come down with crushing nausea, vomiting, and diarrhea, you've probably called it something like the "stomach flu" or a "24-hour bug." While those terms are used a lot, neither one of them is accurate.

Many things can cause stomach flu, but the influenza virus isn't among them. And expecting a 24-hour recovery may be overly optimistic.

This article looks at the symptoms, causes, and treatment of the stomach flu and explains why it's not really a "flu" at all.

African-american woman holds stomach - stock photo

Catherine McQueen / Getty Images

Stomach Flu Symptoms

What we call stomach flu is actually gastroenteritis, also known as infectious diarrhea. It's characterized by inflammation in the stomach and gastrointestinal tract (digestive system).

Gastroenteritis can lead to:

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

Stomach flu generally comes on suddenly and hits hard. Then symptoms gradually decrease as you get better.


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

Common Viral Stomach Flu Causes

Viral gastroenteritis is the most common form. The most common stomach flu viruses include:

  • Rotavirus: Most common in babies between 3 months and 15 months old
  • Norovirus: Most common cause of adult cases
  • Adenovirus: Most common in children under 2
  • Astrovirus: Affects all ages; less severe than rotavirus or norovirus infection

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

These viruses are extremely contagious and easily passed from person to person. Methods of transmission include:

  • Direct contact with a sick person
  • Aerosolized (airborne) particles from vomit
  • Consuming contaminated food and water
  • Fecal-oral route (from not washing hands after defecating, changing diapers, digging in contaminated soil, etc.)

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

Common Bacterial Stomach Flu 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 ten days.

Common Parasitic Stomach Flu Causes

Parasites are less common causes of gastroenteritis. 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 for between two and six weeks.

Is Stomach Flu 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
  • A.k.a. 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

  • A.k.a. 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


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?

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


Symptoms of gastroenteritis 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 (e.g., ibuprofen, naproxen, aspirin) are more likely to upset your stomach
  • Antibiotics can help clear up a bacterial or parasitic infection (they're ineffective against viruses)

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

When to Call a Healthcare Provider

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 Fahrenheit)


Stomach flu is transmitted 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 flu 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.

  • What is the most common cause of gastroenteritis?

    Norovirus is the most common cause of viral gastroenteritis, accounting for about 60% of all cases.

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