What You Should Know About Gastroenteritis

By Kristina Herndon, RN 

 Medically reviewed by Jane Kim, MD

A 24-hour stomach bug is a viral infection that causes diarrhea and vomiting. Most cases are easily treatable and resolve in one to three days.

Sometimes called the "stomach flu," the 24-hour stomach bug is a type of gastroenteritis caused by a contagious infection like norovirus.

This article discusses the 24-hour stomach bug. It explains the causes, diagnosis, and treatment of viral gastroenteritis. It also details why the stomach bug is not the same as the flu and ways to prevent it.

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What Does a 24-Hour Stomach Bug Feel Like?

A 24-hour stomach bug is really viral gastroenteritis—inflammation in your stomach and gastrointestinal tract (digestive system)—that causes diarrhea.

Viral gastroenteritis also leads to other symptoms that include:1

  • Abdominal pain and cramps

  • Fever with or without chills

  • Headache

  • Nausea

  • Vomiting

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

How Long Do Symptoms Last?

Despite being called the 24-hour stomach bug most cases of viral gastroenteritis last longer than a day. Depending on the cause, a stomach bug can linger for up to 10 days.2

What Causes a 24-Hour Stomach Bug?

The stomach bug is usually caused by a virus. Food poisoning, bacterial infections, and parasites can cause similar symptoms and may be mistaken for a 24-hour stomach bug.

Common Viral Causes

Stomach bugs are often caused by viruses. The typical culprits include:3

  • 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 complications4

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.5

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. The following also plays a role:5

  • 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.

How Long Is a 24-Hour Stomach Bug Contagious?

Symptoms usually appear one to three days after exposure to viral gastroenteritis. Depending on the type of virus, the stomach bug can be contagious before symptoms appear and for up to two weeks after you recover. In general, children should be symptom-free for 48 hours before returning to school.6 

Food Poisoning vs. 24-Hour Stomach Bug

Food poisoning is often mistaken for a 24-hour stomach bug but is caused by bacteria or parasites instead of a virus.

Symptoms of food poisoning tend to come on faster than the stomach bug. Diarrhea and vomiting often begin within a few hours of ingesting contaminated food or water.

Bacteria-associated gastroenteritis is primarily related to something you ate and can be caused by:7

  • Campylobacter

  • Escherichia coli (E. coli)

  • Salmonella

These bacterial infections are transmitted through contaminated poultry or other tainted foods, including meat, produce, and dairy products. Campylobacter strains account for around one-third of all bacterial cases.8

Symptoms of bacterial gastroenteritis can last anywhere from one to 10 days and may require antibiotics.

Parasites can also cause similar symptoms. Parasitic infections are spread through contaminated food, water, or soil. The primary culprits of parasite-associated gastroenteritis are:9

  • Giardia

  • Cryptosporidium

Parasitic infections typically take longer to resolve than viral or bacterial gastroenteritis. Symptoms commonly last between two and six weeks.10

Is a Stomach Bug Really the Flu?

When describing a stomach bug, the term "flu" is a misnomer. In medical terms, the flu (influenza) is a common viral respiratory infection. It involves symptoms such as:11

  • Fever

  • Chills

  • Muscle aches

  • Cough

  • Congestion

  • Sore throat

  • Body aches

  • Fatigue

  • Headaches

When you get a flu vaccine, this is what you're being protected from—not gastroenteritis.12

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

Flu

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

Diagnosis

You may know the cause of your symptoms before even seeing a healthcare provider.

For example, if you and several others get sick after eating at a restaurant, food poisoning is a reasonable assumption. If sickness spreads through the household in waves and is going around school, it is likely a viral infection.

Symptoms that aren't severe and only last a few days 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:13

  • Blood tests

  • Stool tests

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.14

Treatment

Symptoms of a 24-hour stomach bug usually go away on their own. The main focus of treatment is to prevent dehydration due to fever, vomiting, and diarrhea.

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These treatments may help to relieve symptoms and prevent complications:

  • Stay hydrated. Water, oral rehydration solutions, and electrolyte-rich sports drinks are good choices, but avoid sugary sodas and fruit juice. Broth or ice pops are also helpful for preventing dehydration.15

  • Follow the BRAT diet—banana, rice, apple, and toast—to ease a queasy stomach and stop diarrhea.16 Other bland foods that can help include saltine crackers and mashed potatoes.

  • Anti-nausea medicines like Reglan (metoclopramide) or Zofran (ondansetron) can be prescribed to reduce vomiting and lessen the risk of dehydration.17

  • Anti-diarrheal medication like Pepto-Bismol (bismuth subsalicylate) or Imodium (loperamide) can be taken to relieve diarrhea, but should not be used in children or if you have bloody stools.15

  • Tylenol (acetaminophen) can be taken to relieve fever; other over-the-counter fever reducers (ibuprofen, naproxen, aspirin) are more likely to upset your stomach.18

Antibiotics are ineffective against viruses that commonly cause the 24-hour stomach bug but may be prescribed to help clear up gastroenteritis caused by bacterial food poisoning.19

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 a 24-hour stomach bug.15

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 the following:18

  • 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)

Additional symptoms in infants and children that warrant a call to your child's pediatrician include:20

  • Crying without tears

  • Diarrhea that lasts longer than two days

  • Dry mouth or cracked lips

  • Eyes appear sunken

  • Inability to keep even small sips of liquid down, lasting more than a few hours

  • Lethargy or the child appears unusually sleepy or less alert

  • No wet diapers for four to six hours in babies or no urination for six to eight hours in older children

  • The soft spot on an infant's skull appears depressed or sunken

 

Summary

A 24-hour stomach bug is a viral infection. It is spread through contact with an infected person, airborne particles, and contaminated surfaces. It can also be transmitted through contaminated water or food. This is not the same as food poisoning, which is caused by a bacterial or parasitic infection.

Common symptoms of the stomach bug include diarrhea, abdominal pain, nausea, vomiting, and fever. Sometimes, the stomach bug may go away after 24 hours. But it may take up to 10 days before you fully recover. People are generally contagious for 48 hours after symptoms resolved, though some viruses can

Treatments may involve medications to stop vomiting and diarrhea, following a bland diet, and ensuring proper hydration. Get medical help for severe symptoms.

Sources

National Institutes of Health, U.S. National Library of Medicine: MedlinePlus. Gastroenteritis.

Australian Government, Depart of Health: healthdirect. Gastroenteritis.

Johns Hopkins Medicine. Understanding viral gastroenteritis.

Vu DL, Bosch A, Pintó RM, Guix S. Epidemiology of Classic and Novel Human Astrovirus: Gastroenteritis and Beyond. Viruses. 2017 Feb 18;9(2):33. doi: 10.3390/v9020033.

Robilotti E, Deresinski S, Pinsky BA. Norovirus. Clin Microbiol Rev. 2015;28(1):134-64. doi:10.1128/CMR.00075-14

Centers for Disease Control and Prevention. How norovirus spreads.

Johns Hopkins Medicine. Bacterial gastroenteritis.

Facciolà A, Riso R, Avventuroso E, et al. Campylobacter: from microbiology to prevention. J Prev Med Hyg. 2017 Jun;58(2):E79-92.

Centers for Disease Control and Prevention. Parasites - giardia.

Medical University of South Carolina: MUSC Health. Gastroenteritis.

Centers for Disease Control and Prevention. Influenza (flu): What you need to know.

Centers for Disease Control and Prevention. Influenza (flu): Misconceptions about flu vaccines.

Cedars Sinai. Bacterial gastroenteritis.

Mount Sinai. Viral gastroenteritis (stomach flu).

National Institutes of Health, National Institute of Diabetes and Digestive and Kidney Diseases. Treatment of viral gastroenteritis ("stomach flu").

American Academy of Family Physicians: familydoctor.org. BRAT diet: Recovering from an upset stomach.

Afacan MA, Tayfur İ. Comparison of the effects of metoclopramide and ondansetron on emergency service observation times in acute gastroenteritis-related nausea and vomiting cases. Sisli Etfal Hastan Tip Bul. 2019;53(2):186-189. Published 2019 Jul 11. doi:10.14744/SEMB.2019.80217

Nemours KidsHealth. Gastroenteritis (stomach flu).

University of Rochester Medical Center. Viruses, bacteria, and parasites in the digestive tract.

Merck Manual (Consumer Version). Gastroenteritis in children. 

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By Kristina Herndon, RN
Kristina Herndon, BSN, RN, CPN, has been working in healthcare since 2002. She specializes in pediatrics and disease and infection prevention.