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Food Poisoning or Stomach Virus? The Telltale Symptoms to Look For

woman with stomach pain running to bathroom

The terms food poisoning, stomach bug, stomach flu, and stomach virus are often used interchangeably, but they’re not the same. A stomach bug or stomach flu is a sickness caused by a virus (the medical term for this condition is viral gastroenteritis). The virus causes an inflammation of the gastrointestinal tract (stomach and intestines). On the other hand, food poisoning occurs after eating contaminated food or spoiled food, caused by foodborne germs. According to the Centers for Disease Control and Prevention (CDC), food poisoning affects some 48 million Americans each year, and it is more common than viral illnesses. 

Please continue reading to learn more about the telltale signs that can help you determine whether you’re dealing with a viral infection or food poisoning.

What are 3 warning signs that food may be bad or have food poisoning?

You should suspect food poisoning if the food looks, tastes, or smells bad. Germs that cause food spoilage often cause food to become slimy or mushy in appearance, develop unpleasant odors, and taste sour or “off.”

How do you tell if you have a stomach bug or something else?

Food poisoning and viral gastroenteritis cause many of the same symptoms. Common food poisoning symptoms such as nausea, vomiting, stomach pain, and diarrhea are also symptoms of stomach flu. So, the truth is that you may never know if you have a stomach virus or food poisoning. However, some clues can help you figure it out (more about this later). 

What are the obvious symptoms of having food poisoning?

The most common food poisoning symptoms include abdominal pain or cramping, diarrhea, and vomiting. Other symptoms of food poisoning can include thirst, headache, low-grade fever, chills, sweating, tiredness, and muscle aches. People with severe symptoms may notice bloody stools or vomit, severe abdominal cramps, and even fainting or loss of consciousness.

What are the symptoms of a stomach bug?

Viral gastroenteritis or stomach bug symptoms are similar symptoms to food poisoning. The symptoms typically include nausea, vomiting, watery diarrhea, and stomach cramps. You can also develop symptoms such as thirst, dry mouth, lightheadedness, tiredness, fever, muscle aches, joint pain, and urinating less than usual.

What is the difference between food poisoning and stomach bug?

Here are some of the critical differences between stomach flu and food poisoning.


  • Viral gastroenteritis is caused by viruses such as norovirus, rotavirus, and other viruses.
  • Food poisoning is caused by foodborne germs, including viruses, bacteria, and parasites. Some of the most common germs that cause foodborne illnesses in the U.S. are norovirus, salmonella, and Staphylococcus aureus (Staph).


  • Symptoms of stomach flu develop 24-48 hours after exposure to the virus.
  • Symptoms of food poisoning develop within a few hours (2-6 hours after eating contaminated food).


  • Doctors usually diagnose a stomach virus based on your symptoms. There is a rapid stool test that can detect norovirus and rotavirus, but it is not available at most health clinics.
  • Food poisoning is diagnosed based on your history and symptoms. A stool test can help to identify bacterial or parasitic infections.


  • You can treat a stomach bug at home by replacing fluids and electrolytes to prevent dehydration and eating bland foods that are easy to digest (a BRAT diet is recommended - bananas, applesauce, rice, and toast). Some over-the-counter medicines can help to relieve your symptoms.
  • Treatment for food poisoning also consists of replacing fluids and electrolytes to stay hydrated and eating easy-to-digest foods. In severe cases, doctors may prescribe antibiotics for certain types of food poisoning. 


  • Viral gastroenteritis is highly contagious, and it spreads via the vomit or feces of an infected person through personal contact. For example, if someone is sick and has not washed their hands thoroughly, they might have the virus on their hands and can transmit it to you when you shake hands. It can also spread through contaminated food and drink or contaminated objects.
  • Food poisoning occurs when you eat contaminated food or drink contaminated water or beverages.


  • You can prevent viral gastroenteritis by washing your hands thoroughly if you’re sick or have been around someone who is sick. There is a vaccine available against rotavirus. 
  • You can prevent food poisoning by keeping your food preparation equipment and surfaces clean, refrigerating perishable foods, eating fully cooked meats and eggs, and discarding foods that appear to be spoiled.

How do I know if it's stomach flu or food poisoning?

Both conditions cause gastrointestinal distress. However, if you have a fever, headache, body aches, and projectile vomiting, you may have a stomach bug or viral gastroenteritis. If you have bloody diarrhea, it could be food poisoning.

The circumstances surrounding your illness can offer clues. If you develop symptoms within a few hours of eating food that may have been spoiled or contaminated, you likely have food poisoning. 

If a family member or friend ate the same food and became sick, that’s another clue that points to food poisoning.

If you have eaten foods that are easily contaminated or spoiled, such as salad greens, undercooked eggs or meat, seafood, raw milk, or dairy products just before your symptoms worsen, it could be food poisoning. 

On the other hand, if you have been around someone who has a similar illness, it could be viral gastroenteritis. For example, if your child is sick and there’s a stomach bug going around your child’s school.

When to see a doctor?

Most people with a food-borne illness get better on their own in 2-5 days without medical treatment. You should see a doctor if:

  • You have a high fever above 104F (40C).
  • You’re not able to keep liquids down for more than 24 hours.
  • You’ve been vomiting for more than 2 days.
  • You have blood in your vomit or bowel movements.
  • You have severe abdominal cramping or abdominal pain.
  • Your symptoms have been going on for more than 7-10 days.
  • You have signs of dehydration such as dry mouth, excessive thirst, dark yellow urine, less frequent urination, lightheadedness or dizziness, and severe weakness.

Keep in mind that while most forms of food poisoning aren’t serious, a type of food poisoning called botulism, which is caused by a bacterium called Clostridium botulinum, can be fatal. This bacterium produces toxins that affect the nervous system. Seek medical attention immediately if you have botulism symptoms such as blurred vision, double vision, drooping eyelids, slurred speech, or other neuromuscular symptoms.


  1. https://www.ucihealth.org/blog/2016/01/stomach-flu-or-food-poisoning
  2. https://ask.usda.gov/s/article/What-are-the-signs-of-food-spoilage#
  3. https://www.cdc.gov/foodsafety/foodborne-germs.html
  4. https://www.niddk.nih.gov/health-information/digestive-diseases/viral-gastroenteritis/symptoms-causes