What’s the Difference Between Norovirus (Stomach Bug) vs. Food Poisoning?

Identifying the cause can help you find treatment

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It can be hard to tell the difference between norovirus (the most common cause of stomach flu) and food poisoning because both cause nausea, vomiting, and stomach pain.

There are a few tell-tale signs that can differentiate the two, including when symptoms start and how long they last. With food poisoning, symptoms tend to develop sooner, usually within a few hours. However, food poisoning symptoms usually don't last as long as the stomach bug.

Norovirus and food poisoning are typically caused by two different things—one by a virus and the other by bacteria—and differ in how they are treated.

This article describes the symptoms, causes, diagnostic tests, and treatments for norovirus vs. food poisoning. It also explains when it is time to see a healthcare provider when symptoms are severe.

Tips to Prevent Food Poisoning - Illustration by Joules Garcia

Verywell / Joules Garcia

Symptoms of Food Poisoning vs. Norovirus

Some of the symptoms of food poisoning are the same as symptoms of norovirus, so it can be difficult to tell the difference based on symptoms alone.

Here is how the two illnesses compare side by side:

Food Poisoning
  • Nausea

  • Vomiting

  • Stomach pain

  • Cramping

  • Weakness

  • Diarrhea (may be watery, bloody, or mucus-like)

  • Fever

  • Nausea

  • Vomiting

  • Stomach pain

  • Cramping

  • Weakness

  • Diarrhea (typically watery)

  • Fever

  • Chills

  • Headache

  • Muscle aches

In a nutshell, flood poisoning and norovirus both cause severe gastrointestinal symptoms, but norovirus (like most communicable viral diseases) typically leads to flu-like symptoms.

On the other hand, food poisoning is more likely to cause severe gastrointestinal symptoms such as projectile vomiting and bloody stools.

How Long Do Symptoms Last?

Most people recover from food poisoning in 12 to 24 hours. People with stomach flu may take longer with symptoms sometimes persisting for more than a week.

Onset of Food Poisoning vs. Norovirus

The biggest difference between food poisoning and norovirus is when symptoms begin. Food poisoning causes symptoms sooner than the stomach bug. This is explained by how both diseases work:

  • With food poisoning, symptoms are caused by the release of enterotoxins by bacteria found in contaminated foods. These toxins directly target and attack the intestines.
  • With norovirus, it is the virus that directly attacks the intestines. But in order to cause significant symptoms, the virus needs to replicate to substantial numbers, and this takes time.

How Soon Do Symptoms Start?

Signs and symptoms of food poisoning usually begin 30 minutes to 8 hours after eating contaminated food. Signs of stomach flu usually start 12 to 48 hours after exposure to the virus.

Causes of Food Poisoning vs. Norovirus

Not only are the organisms that cause food poisoning and stomach flu different but so are some of the ways they are spread.

Causes of Food Poisoning

Food poisoning is caused by eating something that is contaminated with germs, also known as a foodborne illness. This usually involves bacteria like E. coli (Escherichia coli), Staphylococcus aureus, or Salmonella, but there are viruses or parasites that can also cause food poisoning. If the food is not cooked, the germs can be passed to someone who eats the food.

The contamination can occur anywhere from the farm or ranch to the processing facility to the store or delivery service to the home.

Causes of Stomach Bug

Norovirus is the predominant cause of stomach flu in adults, while rotavirus is the most common cause in children. Stomach flu can also be triggered by other viruses, bacteria, or parasites.

With norovirus, the route of transmission is broader because the virus tends to be harder to neutralize on surfaces than foodborne bacteria.

Norovirus is commonly spread through:

  • Contaminated food or drink
  • Touching contaminated surfaces
  • Person-to-person contact with an infected person

How Common Are They?

In the United States, an estimated 48 million people get food poisoning, and up to 21 million get norovirus each year. Combined, they are responsible for tens of thousands of emergency room visits and hospitalizations annually.

Diagnosis of Food Poisoning vs. Norovirus

The diagnosis of food poisoning and norovirus is more or less the same, and many of the tools used for the diagnosis (such as stool cultures) check for both bacterial and viral causes.

If you are suspected of having food poisoning or norovirus, the diagnosis will typically involve:

  • A review of your symptoms
  • A review of your medical history
  • A physical examination
  • A stool culture to check for suspected bacteria or virus

Testing is especially relevant if there is a community outbreak (such as an outbreak on a cruise ship or in a hospital). At other times, testing can help trace the source of food contamination.

On an individual level, the differentiation won't inherently alter how either disease is treated.

With that said, the differentiation may be essential for those who are at high risk of complications, Including:

Treatment of Food Poisoning vs Norovirus

The treatment of food poisoning and the stomach flu are similar. Generally speaking, antibiotics (used for bacterial infections) and antivirals (used for viral infections) are of little help once symptoms start. In some cases, they can make things worse.

For most people, treatment can be delivered at home and may include:

  • Bed rest
  • Ample hydration: With plain water or electrolyte drinks
  • Bland diet: Including soft foods like white bread, applesauce, or bananas
  • Anti-nausea medications: Like Pepto-Bismol (bismuth subsalicylate)
  • Anti-diarrhea medications: Like Imodium (loperamide)
  • Over-the-counter painkillers: Like Tylenol (acetaminophen)
  • Prescription drugs: Like Zofran (ondansetron) or Reglan (metoclopramide) for severe nausea and vomiting

Prevention of Food Poisoning vs. Stomach Bug

Food poisoning generally isn't contagious from person to person in the way that the stomach flu is. Because the modes of transmission are different, there are different precautions you may need to take to avoid getting or spreading these diseases.

Preventing Food Poisoning

To prevent food poisoning, you should as a general rule:

  • Wash your hands and work surfaces before, during, and after preparing food.
  • Separate raw meat, poultry, seafood, and eggs from ready-to-eat foods.
  • Cook food to the right internal temperature to kill potentially harmful bacteria.
  • Keep your refrigerator at 40 degrees F or below.
  • Refrigerate leftovers within two hours of cooking.

Preventing the Stomach Flu

To prevent the spread of norovirus while someone in your home is sick:

  • Wash your hands frequently with soap and water. 
  • Keep your hands away from your mouth.
  • Handle and prepare food safely.
  • Clean and disinfect common surfaces.
  • Wash laundry thoroughly, including towels and bedding.
  • Avoid unnecessary touching of the sick person.

Stay at Home

If you have symptoms of food poisoning or norovirus, stay home and away from others until your symptoms have completely cleared.

When to See Your Healthcare Provider

There are times when you need more than home-based care if you have food poisoning or stomach flu. It's important to know the signs to prevent potentially serious complications like severe dehydration.

If you have food poisoning, seek immediate medical care if you have:

  • Bloody diarrhea
  • Temperature over 102 degrees Fahrenheit
  • An inability to keep liquids down
  • Diarrhea that lasts more than three days

If you have norovirus, seek immediate medical care if you have:

  • Diarrhea lasting more than two days
  • High fever
  • Frequent vomiting
  • Six or more loose stools in one day
  • Severe abdominal or rectal pain
  • Changes in mental state (such as confusion or irritability)
  • Black or tarry stools (indicative of gastrointestinal bleeding)

Watch for Dehydration

Dehydration is common if vomiting or diarrhea persists for more than 24 hours and can quickly turn deadly if left untreated.

Symptoms of dehydration include:

  • Dark or infrequent urine
  • Dry mouth
  • Dizziness
  • Weakness
  • Confusion
  • Fainting
  • Rapid heart rate


Food poisoning and the stomach flu can come with similar symptoms, like nausea and vomiting, but they’re different conditions. Food poisoning is caused by food that's contaminated by bacteria, viruses, parasites, or toxins. The stomach flu is usually caused by norovirus.

Both can typically be treated at home with hydration, over-the-counter medications for symptom relief, and rest. Protect yourself, your loved ones, and your community by practicing good hygiene habits and ensuring foods are prepared and served safely.

If you develop either condition, watch for signs of dehydration. See a healthcare provider if you have a weak immune system, are pregnant or elderly, or you have severe or lingering symptoms.

13 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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  2. National Institute of Diabetes and Digestive and Kidney Diseases. Diagnosis of viral gastroenteritis (“stomach flu”).

  3. Centers for Disease Control and Prevention. Norovirus.

  4. Centers for Disease Control and Prevention. Key facts about food poisoning.

  5. Centers for Disease Control and Prevention. Foodborne illnesses and germs.

  6. Centers for Disease Control and Prevention. Burden of foodborne illness: findings.

  7. Centers for Disease Control and Prevention. Burden of norovirus illness in the U.S.

  8. Switaj TL, Winter KJ, Christensen SR. Diagnosis and management of foodborne illness. Am Fam Physician. 2015;92(5):358-365.

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  10. Centers for Disease Control and Prevention. Preventing norovirus.

  11. MedlinePlus. Food poisoning.

  12. National Institute of Diabetes and Digestive and Kidney Diseases. Symptoms & causes of viral gastroenteritis ("stomach flu").

  13. MedlinePlus. Dehydration.

By Cristina Mutchler
Cristina Mutchler is an award-winning journalist with more than a decade of experience in national media, specializing in health and wellness content.