Food Poisoning or Stomach Virus? How To Spot The Differences

You’ve just enjoyed a leisurely brunch with your friends at the new restaurant in town and are looking forward to a Sunday afternoon nap. But instead, you find yourself doubling over with stomach cramps and feeling nauseous. Could it be food poisoning or is it a stomach bug?

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 inflammation of the gastrointestinal tract (stomach and intestines). This results in symptoms such as stomach pain, nausea, vomiting, and diarrhea.

Food poisoning occurs after consuming contaminated food or drinks. Food poisoning is caused by bacteria, viruses, or parasites.  Salmonella, E. coli, and Campylobacter are some of the common bacteria that contaminate food and cause food poisoning. Additionally, food poisoning can be caused by a viral infection such as norovirus. These are just some of the common germs that can cause food poisoning. 

Key Distinctions of Food Poisoning vs Stomach Bug

Here is a quick overview comparing food poisoning vs stomach flu:

How Do I Know If It's Stomach Flu or Food Poisoning?

Both stomach flu and food poisoning can lead to symptoms such as nausea, vomiting, and diarrhea. Bloody diarrhea can happen with both conditions as a result of severe diarrhea. Additional symptoms like fever and body chills can occur, particularly in cases of food poisoning. The main differences between stomach flu and food poisoning lie in how quickly symptoms appear and how long they last.  

Symptom onset

Food poisoning

• If you develop symptoms within a few hours of eating food, you likely have food poisoning from food that may have been spoiled or contaminated.

• If you were at a family gathering or picnic where everybody shared the same food and then everyone got sick within a few hours with the same symptoms, that’s another clue that points to food poisoning.

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

Stomach flu

• Symptoms such as vomiting and diarrhea start around one to two days after a person comes in contact with the virus. 

Symptom duration

• Food poisoning symptoms come on faster and resolve more quickly than stomach bugs. The duration of food poisoning varies depending on the type of infection, ranging from a few hours to several days. In mild cases, symptoms resolve within 12 to 48 hours.

• Stomach flu can last 3 to 5 days, but in severe cases, it may last up to 2 weeks. 

Which One is More Common?

Food poisoning is a more common illness than gastroenteritis from a viral infection. 

According to the Centers for Disease Control and Prevention (CDC), food poisoning affects some 48 million Americans each year. 

The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) reports that approximately 19 to 21 million cases of norovirus viral gastroenteritis occur in the U.S. each year.

Is It Important to Differentiate Between Food Poisoning and a Stomach Virus?

Treatment for both conditions is similar, and most people recover at home. However, in severe cases, it’s important to distinguish between the two because antibiotic treatment may be needed for certain types of severe food poisoning. 

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Causes of Food Poisoning and Stomach Bug

What Causes Food Poisoning?

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 

• Bacteria such as Bacillus cereus, Campylobacter, Clostridium perfringens, Clostridium botulinum, Eschericia coli (E. coli), Giardia lamblia, Listeria, Salmonella, Shigella, Staphylococcus aureus (Staph), and Vibrio.

• Viruses such as hepatitis A virus, norovirus, and rotavirus.

Food poisoning occurs when you eat food or drink water and beverages that are contaminated with these disease-causing pathogens (germs).

What Causes a Stomach Bug?

Viral gastroenteritis is caused by viruses such as norovirus, rotavirus, enteric adenovirus, and astrovirus. Other viruses like COVID-19 can cause stomach flu symptoms even in the absence of breathing problems. 

Viral gastroenteritis is highly contagious. It spreads easily, especially among people who come in close contact, for example, school children or dormitory residents.

Transmission occurs via the fecal oral route (from the vomit or feces of an infected person through personal or direct contact). For example, if someone is sick and has not washed their hands thoroughly after using the toilet, 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 touched by an infected person.

Common Risk Factors

Risk factors for food contamination and food poisoning include:

• Poor handwashing after using the toilet. Germs from feces can get transferred to your hands and from there to food.

• Unclean food containers and food preparation surfaces. 

• Improper storage of food that leads to spoilage and the growth of germs.

Risk factors for viral gastroenteritis include:

• Poor handwashing after using the toilet or changing diapers.

• Shared personal items such as drinking glasses and utensils.

• Eating food prepared by an infected person.

• Food preparation surfaces or utensils touched by an infected person.

• Contact with laundry or other items belonging to an infected person.

Comparing Symptoms

Food poisoning and viral gastroenteritis cause many of the same symptoms, making it difficult to distinguish one from the other. 

What Are the Symptoms of Food Poisoning?

The most common food poisoning symptoms and telltale signs are abdominal pain or cramping, diarrhea, and vomiting within a few hours of eating. 

Other symptoms of food poisoning can include: 

• Thirst 

• Headache 

• Low-grade fever 

• Chills 

• Sweating 

• Tiredness 

• Muscle aches 

Severe symptoms of food poisoning can include:

• Bloody stool or vomit

• Severe abdominal cramping

• Loss of consciousness

Food poisoning symptoms typically develop within a few hours (usually within 2 to 6 hours of eating contaminated food). Most people recover from food poisoning in 12 to 48 hours.

What Are The Symptoms of a Stomach Bug?

Viral gastroenteritis or stomach bug symptoms are similar symptoms to food poisoning. GI viral illnesses typically cause the following symptoms: 

• Nausea and vomiting

• Stomach cramps

• Flu symptoms like fever, headache, muscle aches, and joint pain 

• Excessive thirst

• Dry mouth

• Lightheadedness

• Tiredness

• Urinating less than usual

Symptoms of stomach flu (viral gastroenteritis) usually develop 1 to 3 days after exposure to the virus. Most people recover from a stomach bug in 1 to 2 days, but sometimes the symptoms can last longer, up to 14 days.

Symptom Severity and Complications

The most common complication from the symptoms of food poisoning or viral gastroenteritis is dehydration due to loss of fluids from the body. Some germs can cause more severe complications, such as:

• Hemolytic uremic syndrome (blood clots in the kidney) from E. coli

• Bacteremia (bacteria in the bloodstream that can spread to other parts of the body)

• Meningitis (inflammation in the brain and spinal cord)

• Sepsis (an abnormal immune system reaction that causes body-wide tissue damage)

A type of food poisoning called botulism, which is caused by a bacterium called Clostridium botulinum, is a serious infection that 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.

Diagnosis

Diagnosis of food poisoning is made based on history and symptoms. Similarly, a primary care provider or gastroenterologist can diagnose a stomach virus based on your symptoms. 

Medical Tests and Procedures Used

A stool test can help to identify bacterial or parasitic infections. There is also a rapid stool test that can detect norovirus and rotavirus, but it is not widely available at most health clinics.

Most people recover at home from food poisoning and stomach virus without needing specific medical treatment. However, an accurate diagnosis and timely treatment are important if the symptoms are severe or last more than a few days.

Treatments

Home Remedies

Treatment for food poisoning consists of replacing fluids and electrolytes to stay hydrated and eating easy-to-digest foods. It may help to take frequent small sips of water and non-caffeinated, non-alcoholic fluids or suck on ice chips.

Similarly, 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.

Read about how to settle an upset stomach.

Medical Treatments 

You can take over-the-counter anti-diarrhea and anti-nausea medicines at home, such as loperamide (Imodium A-D) and bismuth subsalicylate (Pepto-Bismol, Kaopectate) to relieve symptoms. How long does it take for Pepto-Bismol to work?

In a severe case, doctors may prescribe antibiotics for certain types of food poisoning caused by a bacterial infection. 

Monitoring and Follow-Up Care To Prevent Future Occurrences

Most people recover from food poisoning and stomach viruses without long-term health problems, and no further care is needed. To prevent future recurrences, take hand hygiene and food storage and handling precautions and avoid contact with sick people. 

When To Seek Professional Help

Most people with a foodborne 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.

In addition, certain people are at a higher risk of more severe symptoms and potentially life-threatening complications from food poisoning and stomach flu, such as pregnant people, babies and young children, older adults above age 65, and those with a weakened immune system. These individuals should call their healthcare provider or seek urgent care and expert advice at the first sign of symptoms of stomach bug or food poisoning.

Tips for Preventing Food Poisoning

You can prevent food poisoning by: 

• Keeping your food preparation equipment and surfaces clean.

• Refrigerating perishable foods.

• Eating fully cooked meats and eggs.

• Discarding foods that appear to be spoiled. 

Note: Cross-contamination can occur if fully cooked and uncontaminated food comes in contact with other foods that are raw or contaminated, leading to a physical transfer of bacteria or viruses between foods.

What Are 3 Warning Signs That Food May Be Bad or Cause 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.”

Tips for Preventing the Stomach Bug

You can prevent viral gastroenteritis by washing your hands thoroughly if you’re sick or have been around someone who is sick. 

In addition, it is important to get all recommended vaccinations. There is a vaccine available against rotavirus. Learn more about the rotavirus vaccine.

How to Maintain Gut Health

Here are some daily tips to maintain gut health and prevent infections:

• Eat a healthy diet with a variety of whole foods like fruits, vegetables, legumes, whole grains, nuts, and seeds. These foods are high in fiber, which can help with digestion and reduce the risk of bowel cancer. 

• Take probiotics which contain beneficial bacteria to keep your gut microbiome in balance and prevent overgrowth of harmful bacteria. Probiotic foods include fermented foods like kefir, miso, pickles, and kimchi. You can also eat plain yogurt or take a probiotic supplement.

• Take prebiotics which are dietary fibers that nourish good bacteria in your gut. 

• Reduce stress which can lead to digestive issues. You can try relaxation techniques like meditation, deep breathing, and progressive muscle relaxation. 

• Get enough sleep. Sleep deprivation can negatively affect gut health. 

• Exercise regularly to maintain a healthy body weight and prevent digestive system problems. 

• Limit alcohol and caffeine which can affect digestion. 

• Drink plenty of water. Aim for eight 8-ounce glasses a day. 

• Use antibiotics only when prescribed. Antibiotics can kill good bacteria along with bad bacteria and disrupt the gut microbiome. 

Common Questions

How Long Can Food Poisoning Last?

Food poisoning symptoms last for a few days, usually 2 to 5 days.

What Is The Fastest Way To Flush Out Food Poisoning?

The fastest way to flush out food poisoning-causing germs is to: 

• Hydrate by drinking plenty of water and clear fluids.

• Consume bland foods such as a BRAT diet (bananas, rice, apple sauce, and toast) for faster symptom relief. 

How Long Does It Take To Throw Up After Food Poisoning?

Most people throw up within 2 to 6 hours of eating contaminated food and developing food poisoning. Vomiting can dehydrate you, so it’s important to hydrate by drinking plenty of fluids.