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Stomach Flu (Gastroenteritis)

An intestinal infection causing nausea, vomiting, diarrhea, and stomach cramps. Despite the name, it is NOT caused by the influenza virus and is unrelated to the flu.

Last updated:

Statistics & Prevalence

Acute gastroenteritis is one of the most common illnesses worldwide. In the United States, it causes approximately 179 million episodes per year, resulting in 600,000 hospitalizations and about 5,000 deaths annually. Globally, gastroenteritis kills approximately 1.5-2.5 million people per year, primarily children under 5 in developing countries. Norovirus is the leading cause of foodborne illness outbreaks in the US, responsible for 19-21 million cases annually. The rotavirus vaccine has reduced child hospitalizations by over 80%.

What is Stomach Flu (Gastroenteritis)?

Gastroenteritis, commonly called "stomach flu" or "stomach bug," is an infection and inflammation of the stomach and intestines. Despite its nickname, it has nothing to do with influenza (the flu), which is a respiratory illness. **Key Facts:** - **Cause:** Viruses (most common), bacteria, or parasites - **Main symptoms:** Vomiting, diarrhea, stomach cramps, nausea - **Duration:** Usually 1-3 days for viral; bacterial may last longer - **Biggest risk:** Dehydration, especially in young children, elderly, and immunocompromised - **Contagious:** Highly contagious; spreads easily in families, schools, and cruise ships **Most Common Causes:** 1. **Norovirus** — #1 cause in adults, extremely contagious 2. **Rotavirus** — Was #1 in children before vaccine 3. **Adenovirus** — Common in children under 2 4. **Bacterial** — Salmonella, E. coli, Campylobacter (from contaminated food/water) **Important:** The term "stomach flu" is misleading — this condition is NOT related to influenza.

Common Age

Affects all ages; most severe in young children (under 5), elderly (over 65), and immunocompromised individuals

Prevalence

179 million episodes/year in the US; 19-21 million norovirus cases/year; one of the most common illnesses worldwide

Duration

Viral: 1-3 days typically. Bacterial: 2-7 days. Parasitic: weeks without treatment. Contagious for at least 48 hours after symptoms resolve.

Why Stomach Flu (Gastroenteritis) Happens

**How Gastroenteritis Develops:** **1. Pathogen Entry:** Viruses, bacteria, or parasites enter the body through the mouth — from contaminated food, water, hands, or surfaces. Norovirus requires only a tiny dose (as few as 18 viral particles) to cause infection. **2. Intestinal Infection:** The pathogen infects the lining of the stomach and intestines, triggering inflammation. This disrupts normal fluid absorption, leading to diarrhea and vomiting. **3. Immune Response:** Your immune system fights the infection, causing fever, fatigue, and body aches. Vomiting and diarrhea are also defense mechanisms to expel the pathogen. **4. Dehydration Risk:** The combination of vomiting and diarrhea causes rapid fluid and electrolyte loss. This is the primary danger — dehydration can become serious quickly, especially in young children and elderly. **Risk Factors:** - Close contact with infected individuals - Eating at restaurants with poor food handling - Daycare centers, nursing homes, cruise ships, dormitories - Travel to developing countries - Weakened immune system - Young children and elderly (highest complication risk) - Not washing hands before eating or after bathroom use

Common Symptoms

  • Watery diarrhea
  • Nausea and vomiting
  • Stomach cramps and abdominal pain
  • Low-grade fever
  • Loss of appetite
  • Headache
  • Muscle aches and body pain
  • Fatigue and weakness
  • Chills
  • Bloating

Possible Causes

  • Norovirus (leading cause in adults)
  • Rotavirus (leading cause in unvaccinated children)
  • Adenovirus (types 40 and 41)
  • Salmonella (from contaminated food)
  • E. coli (from undercooked meat)
  • Campylobacter (from undercooked poultry)
  • Contaminated food or water
  • Fecal-oral transmission
  • Contact with infected person or surfaces

Note: These are potential causes. A healthcare provider can help determine the specific cause in your case.

Quick Self-Care Tips

  • 1Stay hydrated — sip small amounts of water or electrolyte solution frequently
  • 2Use Pedialyte for children; diluted sports drinks for adults
  • 3Start with bland foods (BRAT: bananas, rice, applesauce, toast) when ready
  • 4Rest as much as possible
  • 5Avoid dairy, caffeine, alcohol, and fatty foods until recovered
  • 6Wash hands thoroughly with soap and water (not just hand sanitizer)
  • 7If vomiting, try sucking on ice chips for slow hydration
  • 8Don't take anti-diarrhea medication if you have bloody stool or high fever
  • 9Stay home until 48 hours after symptoms stop to prevent spreading

Disclaimer: These are general wellness suggestions, not medical treatment recommendations. They may help manage symptoms but should not replace professional medical care.

Home Remedies & Natural Solutions

1

Oral rehydration at home

Mix 6 teaspoons sugar and 1/2 teaspoon salt in 1 liter of clean water for a homemade ORS. Sip small amounts frequently. Commercial solutions like Pedialyte are preferred when available.

2

BRAT diet

When ready to eat, start with Bananas, Rice, Applesauce, and Toast. These bland foods are easy to digest. Gradually add plain crackers, boiled potatoes, and clear soups.

3

Ice chips for nausea

If you can't keep fluids down, suck on ice chips or frozen electrolyte popsicles for slow, steady hydration without overwhelming the stomach.

4

Ginger for nausea

Ginger tea or ginger chews can help settle nausea. Steep fresh ginger in hot water for 10 minutes. Has evidence-backed anti-nausea properties.

5

Rest

Your body needs energy to fight the infection. Rest as much as possible. Avoid strenuous activity until symptoms resolve and you're eating normally.

Note: Home remedies may help relieve symptoms but are not substitutes for medical treatment. Consult a healthcare provider before trying any new remedy, especially if you have underlying health conditions.

Evidence-Based Treatment

**Primary Treatment — Rehydration:** The MOST important treatment for gastroenteritis is preventing and treating dehydration: - **Oral Rehydration Solutions (ORS):** Pedialyte for children, similar solutions for adults - **Small, frequent sips:** Don't gulp — take small amounts every few minutes - **IV fluids:** For severe dehydration or inability to keep fluids down **Symptom Management:** - **Anti-nausea:** Ondansetron (Zofran) by prescription — especially useful in children to allow oral rehydration - **Anti-diarrheal:** Loperamide (Imodium) for adults with non-bloody, non-febrile diarrhea only - **Fever/pain:** Acetaminophen (Tylenol) — easier on the stomach than ibuprofen - **Probiotics:** Saccharomyces boulardii may help shorten diarrhea duration **What NOT to Do:** - Don't take antibiotics (most gastroenteritis is viral) - Don't take Imodium if you have bloody diarrhea or high fever - Don't fast completely — sip fluids even if you can't eat - Don't drink large amounts at once if vomiting

FDA-Approved Medications

Important: The medications listed below are FDA-approved treatments. Always consult with a healthcare provider before starting any medication. This information is for educational purposes only.

Oral Rehydration Solutions (Pedialyte)

The MOST important treatment. Replaces fluids and electrolytes lost through vomiting and diarrhea. Essential for children and elderly.

Warning: Follow mixing instructions exactly for powdered forms. Do not dilute commercial solutions.

Ondansetron (Zofran)

Prescription anti-emetic that stops vomiting. Often used in children to allow oral rehydration and prevent ER visits for IV fluids.

Warning: Prescription only. May cause headache or constipation. Available as dissolving tablet for easier use.

Loperamide (Imodium)

OTC anti-diarrheal that slows intestinal movement. For adults with watery, non-bloody diarrhea without fever.

Warning: Do NOT use with bloody diarrhea, high fever, or suspected bacterial infection. Not for young children without doctor guidance.

Bismuth Subsalicylate (Pepto-Bismol)

OTC for nausea, diarrhea, and stomach upset. Has mild antibacterial properties.

Warning: Do not use in children under 12. Avoid with aspirin allergy. May cause black tongue/stool (harmless).

Lifestyle Changes

  • ✓Wash hands with soap and water for at least 20 seconds before eating and after using the bathroom
  • ✓Clean and disinfect surfaces with bleach-based cleaners after illness
  • ✓Don't share utensils, cups, or towels with sick family members
  • ✓Stay home from work or school until 48 hours after symptoms stop
  • ✓Cook food to proper internal temperatures
  • ✓Refrigerate leftovers within 2 hours
  • ✓Get the rotavirus vaccine for infants as recommended

Risk Factors

  • Close contact with infected individuals
  • Young children (daycare, schools)
  • Elderly adults (nursing homes)
  • Weakened immune system
  • Eating improperly prepared or stored food
  • Travel to developing countries
  • Crowded living conditions
  • Not washing hands regularly
  • Cruise ships and dormitories

Prevention

  • Wash hands thoroughly with soap and water for 20 seconds
  • Alcohol-based hand sanitizers are less effective against norovirus — use soap and water
  • Don't prepare food for others while symptomatic (wait 48 hours after recovery)
  • Clean and disinfect contaminated surfaces with bleach-based cleaner
  • Wash contaminated laundry in hot water
  • Get the rotavirus vaccine for infants (RotaTeq or Rotarix)
  • Cook food thoroughly, especially poultry and eggs
  • Avoid drinking untreated water

When to See a Doctor

Consult a healthcare provider if you experience any of the following:

  • Unable to keep any fluids down for 24 hours (12 hours for children)
  • Signs of dehydration (dark urine, dizziness, dry mouth, no tears)
  • Blood in vomit or stool
  • Fever above 104°F (40°C)
  • Severe abdominal pain (not just cramping)
  • Symptoms lasting more than 3 days without improvement
  • Confusion or extreme lethargy
  • Pregnant, elderly, or immunocompromised with worsening symptoms
  • Infant under 3 months with vomiting or diarrhea

Talk to a Healthcare Provider

If your symptoms are persistent, severe, or concerning, please consult with a qualified healthcare professional for proper evaluation and personalized advice.

Frequently Asked Questions about Stomach Flu (Gastroenteritis)

Click on a question to see the answer.

No. The "stomach flu" (gastroenteritis) is completely different from influenza. Influenza affects the respiratory system (nose, throat, lungs). Gastroenteritis is an intestinal infection causing vomiting and diarrhea, usually caused by norovirus or rotavirus. The flu vaccine does NOT protect against the stomach flu.

You are most contagious while symptomatic and for at least 48 hours after symptoms stop. With norovirus, you can shed the virus for 2 weeks or more after recovery. Practice hand hygiene even after feeling better.

Go to the ER if you cannot keep fluids down for 24 hours (12 hours for children), have signs of severe dehydration, see blood in vomit or stool, have fever over 104°F, or have severe abdominal pain.

No, most gastroenteritis is viral, and antibiotics don't work against viruses. Antibiotics are only appropriate for confirmed bacterial gastroenteritis. Taking unnecessary antibiotics can worsen diarrhea and contribute to antibiotic resistance.

Focus on hydration — small, frequent sips of water or electrolyte solutions. Rest as much as possible. Once vomiting subsides, start with bland foods. Avoid dairy, caffeine, alcohol, and fatty foods. Most viral gastroenteritis resolves within 1-3 days.

More Digestive Issues Conditions

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Bloating
Constipation
Diarrhea
Nausea
View all Digestive Issues conditions →

References & Sources

This information is based on peer-reviewed research and official health resources:

  • 1

    Norovirus

    Centers for Disease Control and Prevention (CDC)

    View Source
  • 2

    Viral Gastroenteritis (Stomach Flu)

    Mayo Clinic

    View Source

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Medical Disclaimer

The information on this page is for educational purposes only and is not intended as medical advice. It should not be used for self-diagnosis or self-treatment. Always seek the guidance of a qualified healthcare professional with any questions you have regarding a medical condition. If you are experiencing a medical emergency, call your local emergency services immediately.

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This content is for educational purposes only.

Not a substitute for professional medical advice.