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Food Poisoning or Stomach Bug: Decode Your Symptoms

How they differ and when to see a doctor


spinner image woman in a pink sweater holding her side in pain from stomach flu or food poisoning while sitting on a couch with pink patterned pillows
Grace Cary / Getty Images

Feeling queasy, cramping and suddenly turned off by your go-to comfort food? It could be food poisoning or the equally unwelcome stomach bug that’s causing the discomfort. Decoding the culprit behind your stomach woes may be a perplexing and concerning journey.

While a definitive diagnosis requires a medical test, here's everything else you need to know — from the initial onset of symptoms to effective treatments and preventive measures to keep others from falling ill. ​

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What causes food poisoning?

Certain foods are more likely to contain germs that make you sick. They include undercooked animal products (meat, chicken, poultry, eggs), raw milk, seafood, raw vegetables, grains, fruits and flour.

Consuming contaminated food, like those with bacteria such as E. coli or salmonella, can lead to varying symptoms and severity of illness.

Those at higher risk for serious illness include adults aged 65 and older, children younger than five, people with weakened immune systems and pregnant women.

Although most have mild infections, some cases can become serious or even life-threatening. They may lead to other health problems such as meningitis, kidney damage, hemolytic uremic syndrome, arthritis and brain or nerve damage.

Each year, about one in six Americans get sick from food poisoning, resulting in approximately 128,000 hospitalizations and 3,000 deaths, says the Centers for Disease Control and Prevention (CDC).

What causes the stomach bug?

A stomach bug is a virus that spreads from person to person, typically because they do not wash their hands. Even though it is often referred to as the stomach flu, it’s different from influenza, which attacks the respiratory system.

The two most common stomach viruses — also referred to as viral gastroenteritis — are:

  • Norovirus, or the cruise ship virus. It can spread very quickly, especially in isolated environments.
  • Rotavirus, which commonly infects children ages 3 months to 35 months, particularly those in childcare settings. But older adults and those who care for young children are also at risk. Infections are most common in winter and spring.  

Stomach bugs can spread by coming in contact with surfaces, food or air that an infected person has contaminated, typically within close quarters.

Most norovirus outbreaks occur from November to April and on average cause 19 to 21 million illnesses a year, including 109,000 hospitalizations, 465,000 ER visits and 900 deaths, mostly among those age 65 and older, says the CDC.

Onset of symptoms: Food poisoning versus stomach bug

Determining whether you have food poisoning or the stomach flu often hinges on how soon symptoms started after exposure and how long they last.  

Food poisoning symptoms can arise from within a couple of hours to around a week and have a shorter duration than the stomach bug, depending on how quickly your body can flush out the toxins. But remember: The incubation period before symptoms arise can vary depending on the specific germ to which you are exposed.

When a toxin is ingested, it replicates itself in the gastrointestinal (GI) tract, and the body responds by trying to get rid of it through vomit or diarrhea.

“Pathogens like E coli, salmonella, listeria — those are the ones that can cause major complications if they're not caught early for some people,” says Mitzi Baum, chief executive officer at Stop Foodborne Illness, a nonprofit dedicated to the prevention of illness and death from foodborne pathogens.

Conversely, stomach bug symptoms usually appear a day or two after exposure and can last from a few days to approximately a week.

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How to prevent food poisoning

If you have food poisoning, it's likely your family members may also be sick if they ate the same food. To prevent infection, it’s most important to follow standard food safety tips like washing hands and surfaces often, avoiding cross-contamination with raw ingredients, cooking food to the recommended internal temperature and refrigerating food promptly.

If you are able to pinpoint which food in your home made you sick, make sure to throw it out to avoid additional infections.

Infection may also spread from one person to another through contact with an infected person’s vomit or stool that lingers on surfaces or fingers and then transfers to another person’s food or mouth, according to the Cleveland Clinic.

If you think you or someone you know got sick from food poisoning, report it to your local health department, even if you aren’t sure which food infected you. Doing so can help public health officials identify a foodborne outbreak and prevent others from getting sick.

Is the stomach bug contagious?

If someone is sick with a stomach bug, they should prioritize frequent handwashing, isolate themselves in a dedicated room at home, avoid preparing food for others, use bleach to clean contaminated surfaces and thoroughly wash potentially contaminated laundry.

“The stomach bug is very, very contagious,” says Heather Viola, D.O., a primary care physician at Mount Sinai Doctors-Ansonia in New York City.

It only takes as few as 18 viral particles to make a person sick. Although norovirus is most contagious when someone has symptoms, it can still spread through tiny amounts of stool or vomit from an infected person. However, there is a chance infection can spread, even if a person doesn’t exhibit symptoms either before or after their illness peaks, says the CDC.

Keep in mind that the virus can survive on foods in freezing temperatures and up to 140°F. It also has the potential to linger on countertops and serving utensils for up to two weeks and may be resistant to common disinfectants and hand sanitizers.

Symptoms of food poisoning versus stomach bug

While the symptoms of both illnesses overlap, typically food poisoning presents vomiting first.

“Even though we may not realize it’s a toxin, the body does,” says Lisa Ganjhu, D.O., a gastroenterologist at NYU Langone Health in New York City. “It understands that something’s awry, whether it’s a food intolerance or an actual real toxin.”

Once diarrhea occurs, that means a toxin has entered the GI tract.

“That expulsion at both ends causes the cramping and that volatile ejection from your body,” Ganjhu adds. “The GI tract contracts, and all this fluid gets in there to allow the toxin to come out.”

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Food poisoning symptoms

  • Diarrhea
  • Stomach pain or cramps
  • Nausea
  • Vomiting
  • Fever
  • Severe symptoms may include vomiting so often you can’t keep liquids down, bloody diarrhea, dehydration, a fever above 102°F. or diarrhea for more than three days.  

Symptoms of the stomach bug

  • Diarrhea
  • Vomiting
  • Nausea
  • Stomach pain
  • Fever
  • Headache
  • Body aches

How to treat food poisoning or the stomach flu

If you can manage your symptoms at home, it's most important to stay hydrated.

“Usually both the stomach bug and food poisoning can be treated at home. Most people can get away just resting and hydrating with lots of fluids,” says Viola.

Reach for drinks such as Pedialyte, diluted sports drinks or juice.

Another drink that can help prevent dehydration involves combining a hint of sugar, a dash of salt, and a squeeze of any citrus fruit into a glass of water, Ganjhu suggests.

“Every time you have a bowel movement, try to keep some sort of hydration,” says Ganjhu. “When I say hydration, I don’t just mean water. Have some sort of electrolyte water."

However, you will want to avoid taking an antidiarrheal that contains ingredients such as loperamide because it will delay the toxins from leaving your body. Other over-the-counter medications such as bismuth subsalicylate (Pepto-Bismol and similar medications) can help with nausea and sour stomach, Ganjhu adds.

When to see a doctor

With either condition, if you have diarrhea, nausea or vomiting that lasts for more than two to three days, a fever above 102°F, blood in your stool or signs of dehydration, you should call your doctor.

Symptoms of dehydration include a decrease in urination, feeling dizzy when standing up, dry mouth and throat, weakness, confusion, blurred vision and even passing out.  

“Individuals have to be their own best advocate. If you have been vomiting and have diarrhea for more than 72 hours, you need to have tests for foodborne illnesses,” says Baum. “Many medical professionals won’t run them, and you need to be aware of whether you consumed something that was recalled due to some type of bacterial contaminant.”

Typically, older adults and individuals with compromised immune systems often require intravenous (IV) fluids as the initial course of action during a hospital visit. Subsequently, a stool study is recommended to identify the underlying cause of distress. In cases of food poisoning, an antibiotic or antiparasitic treatment may be administered. Alternatively, you may receive a prescription for an anti-cramping medication or be advised to undergo a computed tomography (CT or CAT) scan to assess the level of inflammation in the gastrointestinal tract.

For those who can’t get to an ER, some urgent care units can administer an IV to treat dehydration and may be able to provide a GI pathogen panel.

After recovering from food poisoning

Some people who recover from food poisoning, particularly in severe cases, might encounter mental hurdles when they return to normal eating habits.

“Even though the symptoms are gone, and you might have physically recovered from a severe foodborne illness, there are a lot of emotional scars that linger, because you have to eat every day,” says Baum. “But if something you ate almost killed you, it’s very, very difficult to go back to being carefree.” 

The nonprofit Stop Foodborne Illness offers a resource center to help those who are struggling readjust to regular eating habits and provides additional information to help people navigate a food poisoning diagnosis.

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