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Is It Stomach Bug, Stomach Flu, or Food Poisoning?

Man lying on couch clutching stomach

Your stomach is in knots as another wave of nausea strikes, sending you to the bathroom for the third time in an hour. But what’s the cause? Two likely culprits are stomach bug (also called stomach flu) and food poisoning. But how does stomach flu differ from food poisoning? Understanding the difference may lead to feeling better sooner and even prevent the illness from occurring in the first place.

Stomach Flu and Food Poisoning Defined

Stomach flu and stomach bug are informal terms for viral gastroenteritis, a sickness in which a viral infection causes inflammation in the stomach and intestines. “The term ‘stomach flu’ can be misleading,” says UH internal medicine specialist Christopher Thomas, DO, “because the illness in not caused by influenza, which attacks the respiratory system.”

Though it shares a number of symptoms with viral gastroenteritis, food poisoning is a condition caused by the consumption of contaminated food or water. In fact, food poisoning is an umbrella term for any of the more than 250 foodborne/waterborne illnesses researchers have identified to date.

Comparison of Symptoms

Common symptoms of viral gastroenteritis include:

  • Nausea and/or vomiting
  • Diarrhea
  • Stomach cramps, muscle aches or weakness
  • Loss of appetite
  • Low-grade fever
  • Headaches
  • Light-headedness or dizziness

Common symptoms of food poisoning include:

  • Stomach or intestinal cramping
  • Diarrhea
  • Fatigue
  • Fever
  • Chills and muscle aches
  • Headaches
  • Sweating
  • Thirst

Most people develop viral gastroenteritis symptoms within 24 to 72 hours of exposure to a virus, while food poisoning symptoms can appear anytime within a few hours to weeks following exposure to a foodborne or waterborne pathogen.

Different Causes

Several viruses are the cause of viral gastroenteritis, among them norovirus, rotavirus, adenovirus and astroviruses.

“The most common way to contract stomach flu is through direct contact with someone who is already sick,” Dr. Thomas says. “You can also get a stomach bug by touching any surface that has been in contact with the stool, saliva or vomit of someone infected with the virus.”

By contrast, the cause of food poisoning is consumption of food or water contaminated by bacteria, certain viruses, and less commonly, parasites.


“In the case of viral gastroenteritis,” Dr. Thomas says, “we usually can make a diagnosis based on the presenting symptoms alone.” Also, although not readily available in all clinical settings, a rapid stool test is available for the detection of rotavirus and norovirus.

If food poisoning is suspected, your doctor can often make a diagnosis based on your symptoms, how long you’ve been sick and the specific foods you’ve eaten recently. Depending on your symptoms, your doctor may order certain diagnostic tests.


If the cause of your stomach illness is viral, the treatment is to increase fluids, replenish electrolytes, get rest, and take over-the-counter medicines to reduce fever while the virus runs its course. Most cases of the stomach flu resolve within a few days, though people can feel sick for as many as 10 days or more.

Treatment for food poisoning typically depends on the specific pathogen involved and the severity of symptoms. In most cases, food poisoning resolves without treatment after just a few days, though it can persist longer. Treatment can include replacement of lost fluids and electrolytes and taking doctor-prescribed antibiotics. Also, anti-parasitic medications are available to treat certain foodborne parasites.

A few simple things that you can do at home to speed your recovery from both viral gastroenteritis and food poisoning are:

  • Eat a bland diet to allow your stomach to settle by avoiding solid foods until you feel better
  • Drink plenty of liquids
  • Gradually ease back into eating solid foods, starting with bland, easy-to-digest foods
  • If your illness was severe, avoid dairy products, caffeine, alcohol, sugar, and fatty or highly seasoned foods for a few days to a week following the resolution of your symptoms

When to Call Your Doctor

Food poisoning and viral gastroenteritis can become severe enough to require medical attention. “However,” Dr. Thomas says, “in most cases, people can effectively manage either condition with proper rest, hydration and at-home medical treatment. But call your doctor if you’re unsure what’s causing your symptoms or if you’re having high or persistent fevers.”

Also keep in mind that other health issues can mimic the symptoms of viral gastroenteritis or food poisoning. Call your doctor if your symptoms worsen or if you experience any of the following:

  • Bloody stool or bloody vomit
  • Inability to keep any fluids down
  • Diarrhea lasting more than three days
  • Fever above 104 degrees 
  • Severe abdominal pain

Related Links

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