Is it a stomach bug or flu?

Spot flu symptoms, how it’s different from a stomach bug and how to treat both.

Author: Lynne Choate

Published: February 21, 2018 | Updated: February 12, 2024

We all know someone who has been impacted by the flu. But sometimes what we call the flu really is a stomach bug, and vice versa. How can you tell the difference?

“Many people use the term ‘flu’ to refer to a wide range of illnesses,” said Rachel Alexander, APRN, nurse practitioner with Norton eCare. “With influenza, we tend to have more upper respiratory symptoms but can have stomach issues as well, making you feel very ill.”

Flu symptoms and how it spreads

The flu is a contagious respiratory illness caused by the influenza virus. It infects the nose, throat and sometimes lungs.

Symptoms of the flu can include:

  • Fever
  • Cough
  • Sore throat
  • Runny or stuffy nose
  • Body aches
  • Headache
  • Chills
  • Fatigue
  • Sometimes diarrhea and vomiting

People with flu spread the virus through tiny droplets when they cough, sneeze or talk. These droplets can land in the mouths or noses of people who are nearby. The flu virus also can live on surfaces such as shopping carts and doorknobs.

Germs make their way into the body and can lead to illness when someone gets the virus on their hands, then touches their eyes or mouth.

Antiviral medication can treat flu symptoms. It is most effective if taken within the first 24 to 48 hours of flu symptoms and will help lessen the severity.

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Or is it a stomach bug?

Medically speaking, a gastrointestinal virus often is associated with norovirus and is not the same as the flu virus.

Symptoms of norovirus can include:

  • Diarrhea
  • Throwing up
  • Nausea
  • Stomach pain
  • Sometimes fever, headache and body aches

Symptoms usually develop 12 to 48 hours after exposure, and most people will experience the symptoms for one to four days.

Unfortunately, the only treatment for a norovirus stomach bug is supportive care that includes staying hydrated, eating a bland diet and resting. The virus has to run its course. If symptoms worsen or persist, seek medical attention.

A common concern with both illnesses can be dehydration, so it’s important to drink lots of fluids.

“Fluid intake and rest are important with any virus,” Alexander said. “We recommend that you avoid caffeinated drinks, drinks high in sugar and dairy products if you are experiencing vomiting and diarrhea.”

Flu symptomsNororvirus symptoms
FeverDiarrhea
CoughThrowing up
Sore throatNausea
Runny or stuffy noseStomach pain
Body achesSometimes fever, headache and body aches
Headache 
Chills 
Fatigue 
Sometimes diarrhea and vomiting 

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