A stomach virus, sometimes called stomach flu, refers to a viral infection of the digestive tract. Food poisoning is a bacterial infection that enters the body in food. Both can cause abdominal symptoms.

Bacterial and viral infections have similar symptoms, such as nausea, vomiting, and diarrhea, but a stool test may distinguish between them.

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A viral infection that attacks the digestive system is commonly called a stomach virus.

People sometimes call the illness a ‘stomach flu‘, although this name is misleading, as influenza attacks the respiratory system. A stomach virus can also be known as viral gastroenteritis.

Different strains of the virus exist. According to the Centers for Disease Control and Prevention (CDC), the most common cause in the United States is norovirus.

Food poisoning, on the other hand, describes the ingestion of contaminated food. Bacteria, viruses or less commonly parasites can enter the body and cause symptoms of gastroenteritis through food that has spoiled, been unhygienically prepared or contaminated in any other way.

Stomach viruses

Stomach viruses are highly contagious and can spread quickly. People infected with a stomach virus are contagious from the moment they begin feeling ill and also for the first few days after they recover.

A stomach virus can spread in several different ways:

  • eating food or drinking liquids that have been contaminated with the virus
  • having direct or indirect mouth contact with an infected person or surface with the virus on it

The virus also inhabits the vomit and stools of people who have the infection.

Food poisoning

Cross-contamination is often the cause of food poisoning, during which harmful organisms transfer from one surface to another. Uncooked and ready-to-eat foods, such as salads, are particularly at risk of contamination.

Each year, approximately 48 million people in the United States experience a bout of food poisoning.

Bacteria can grow rapidly when a range of foods, including meats, dairy products, and sauces, are not kept at the right temperature. Bacteria and other harmful organisms produce poisonous substances that can cause inflammation of the intestines when eaten.

Contamination can also occur at home if raw meat is not handled or cooked properly.

Salmonella and E. coli are two common types of bacteria linked to food poisoning.

The symptoms of stomach viruses and food poisoning are very similar but there can be some differences.

Stomach viruses

The symptoms of a stomach virus include:

  • diarrhea that may be watery or bloody
  • a loss of appetite
  • nausea or vomiting
  • stomach cramps, muscle aches, or weakness
  • low-grade fever
  • headaches
  • light-headedness or dizziness

A stomach virus does not usually cause bloody stools. Stools that contain blood could signal a more serious infection.

These symptoms often last 3-4 days but can last for up to 14 days.

Food poisoning

Symptoms of food poisoning can occur within hours of eating. People may experience:

  • watery or bloody diarrhea
  • nausea
  • vomiting
  • stomach pain and cramping
  • a fever, chills, and body aches
  • dizziness and lightheadedness from dehydration

Sickness from food poisoning can last from a few hours to several days.

People can usually suspect food poisoning if they ate unrefrigerated food or other individuals who consumed the same food are experiencing similar symptoms.

Salads, raw or undercooked poultry, eggs, seafood, and other dairy-based products are high-risk foods for food poisoning.

There is no single method for diagnosing a stomach virus. A doctor will likely base a diagnosis on the presenting symptoms alone.

A rapid stool test can be used to detect the rotavirus or norovirus but it is not readily available at most clinics. There are no quick tests for other viruses. A stool sample can also be used to rule out bacterial or parasitic infection.

Diagnosing food poisoning can be difficult, especially if you cannot identify the particular cause. Stool tests may be able to identify the disease-causing pathogen.

Treatment depends on the organism causing the infection.

Supportive therapy that includes increased hydration, rest, electrolyte replenishment, and medication for fever, are usually all that’s needed for viral illnesses. This is because viruses do not respond to antibiotics and simply need to run their course.

If it is determined that a bacteria, like Salmonella, is causing the symptoms, an antibiotic may be prescribed. For parasites, anti-parasitic medications may be available.

There are a few steps people can take at home to aid recovery from a stomach virus or food poisoning.

  • Let the stomach settle. Try not to eat any solid foods until you feel better.
  • Suck on ice chips or take small sips of water. People should drink plenty of liquids to prevent dehydration. Avoid juices or other beverages with a lot of sugar or sweeteners that can make diarrhea worse.
  • Ease yourself back into eating. Start with bland, easy-to-digest foods, such as soda crackers, toast, and rice. Stop eating if a feeling of nausea returns.
  • Avoid certain substances until feeling better, or for a few days to a week after symptoms have resolved cleared if your case was severe. These include dairy, caffeine, alcohol, sugar, and fatty or highly seasoned foods.

People should be cautious of taking over-the-counter (OTC) medications, unless advised by a healthcare provider, as some can worsen the infection. Even anti-diarrhea medications can make the situation worse in some cases.

Gastroenteritis will typically resolve within a few days or less without medication. However, hydration is vital to a speedy recovery and prevention of complications.

People should seek medical attention if they have have any of the following symptoms:

  • bloody stool or vomit
  • unable to keep liquid down for 12-24 hours
  • dizziness or lightheadedness
  • fever above 104 °Fahrenheit (°F)
  • severe, unrelenting abdominal pain

Stomach virus

The CDC estimate that norovirus causes 19 to 21 million illnesses each year. The following preventive measures can help reduce the risk of catching a stomach virus.

  • Practicing proper hand hygiene: People should always wash their hands with soap and water, especially after using the toilet, changing diapers, or before eating or preparing food.
  • Taking precautions when in the kitchen: It is important to rinse fruits and vegetables and cook all food thoroughly.
  • Cleaning and disinfecting potentially contaminated surfaces: People should immediately clean and disinfect contaminated surfaces after vomiting or diarrhea.
  • Washing laundry thoroughly: The stomach virus can easily be carried from person to person so any clothing contaminated with vomit or stool should be removed and washed in hot water.
  • Keeping a distance from anyone who is infected with the virus: If someone in a household is infected, they should use separate personal items such as plates and glasses, and use a separate bathroom if possible.

There is a vaccination available in some countries that counters certain stomach viruses. The vaccine can be effective in helping to prevent severe symptoms of the virus when given to children in the first year of their life.

Food poisoning

People can help prevent food poisoning by ensuring that meats, salads, dressings, and other foods are stored at the right temperature. Do not eat food that has been left out of storage for more than 2 hours.

It is important that people wash their hands when handling any raw meat. They should also make sure to cook it thoroughly, and to avoid eating raw meat, raw eggs, or sauces made with raw eggs. During picnics or parties, food that should be refrigerated should be kept on ice.

People should also be careful when eating in restaurants or other unfamiliar environments.

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What should a person do when they have food poisoning instead of a stomach virus?


Food poisoning usually resolves by itself in a few days.

In most cases, it is usually enough to take plenty of rest, stay isolated and hygienic, and drink enough fluids. In some severe cases though, specific therapies may be needed like anti-nausea, antibiotic, and anti-diarrhea medications.

Saurabh Sethi, MD, MPHAnswers represent the opinions of our medical experts. All content is strictly informational and should not be considered medical advice.
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