What Is the “Stomach Flu” (Acute Gastroenteritis)?

Acute gastroenteritis is an inflammation of the lining of the intestines. It is most commonly caused by viruses, particularly norovirus, which is responsible for hundreds of millions of cases worldwide each year. Despite the nickname “stomach flu,” it is not related to influenza and does not affect the respiratory system.

Viral gastroenteritis is highly contagious and can spread through close contact with an infected person, contaminated surfaces, or consuming contaminated food or liquids. It tends to peak during winter and spring months and can develop quickly, lasting anywhere from overnight to up to 10 days in more severe cases.

Different Causes: Bacterial vs. Viral

Food Poisoning:
Most true cases of food poisoning are caused by bacteria such as E. coli or salmonella. This often happens through cross-contamination, improper food handling, or food left in warm, moist environments where bacteria can grow.

Stomach Virus (Gastroenteritis):
The stomach bug is viral in nature, commonly caused by norovirus. It spreads easily from person to person and through contaminated food, drinks, or surfaces.

Similar Symptoms—But Some Key Differences

Food poisoning and infection from stomach viruses can cause similar symptoms in patients, such as nausea, vomiting and diarrhea. However, there can be additional varying symptoms of each illness to look out for.

Symptoms of Food Poisoning may include:

• Stomach pain and cramping
• Fever
• Nausea and vomiting
• Diarrhea
• Bloody stool (a potential sign of serious infection)

Symptoms of a Stomach Virus may include:

• Watery or loose stools
• Loss of appetite
• Muscle aches
• Fatigue or weakness
• Low-grade fever
• Headache or dizziness

Severe symptoms of gastroenteritis that require medical attention include:

• Fever of 101°F or higher
• Severe or persistent diarrhea or vomiting (risk of dehydration)
• Difficulty swallowing or breathing
• Severe headache

Food Poisoning Comes On Fast

Food poisoning usually hits hard and quickly. Symptoms often appear within six hours of eating contaminated food. If multiple people become sick after eating the same meal, food poisoning is more likely the cause.

Stomach Viruses Tend to Last Longer

Food poisoning is miserable, but it often runs its course within 24–36 hours and usually resolves within a few days. A stomach virus, however, may linger for several days and, in some cases, up to 10 days, especially in children or those with weakened immune systems.

Both Can Lead to Dehydration

Whether you’re dealing with food poisoning or a stomach virus, dehydration is the biggest concern—especially for children, older adults, and those with chronic conditions.

Signs of dehydration include:

• Increased thirst
• Dry mouth
• Headache or dizziness
• Fatigue
• Decreased urine output

To stay hydrated:

• Drink plain water or electrolyte drinks (Gatorade, Pedialyte for children)
• Avoid caffeinated beverages
• Take small, frequent sips if nausea is severe

Diagnosing and Treating Stomach Illness

In most cases, both food poisoning and viral gastroenteritis improve with:

• Rest
• Rehydration (sports drinks, broth, or oral rehydration solutions)
• A bland diet such as the BRAT diet (bananas, rice, applesauce, toast)

If nausea prevents you from keeping fluids down, a provider may recommend medication to control vomiting or, in more serious cases, IV fluids to prevent dehydration.

When to Seek Medical Care

While most cases resolve on their own, seek medical attention if you or a family member experiences:

• Persistent vomiting or diarrhea
• Signs of dehydration
• High or prolonged fever
• Bloody stool
• Difficulty breathing or swallowing

We’re Here to Help

Whether you’re dealing with food poisoning or the dreaded stomach flu, ConvenientMD can help. We regularly treat acute gastroenteritis (including norovirus) and food-related illness, ensuring you or your family member gets the right care to recover safely. Just walk into any ConvenientMD—no appointment needed.