Stomach Flu vs. Food Poisoning: What’s the Difference?

When it comes to the stomach bug vs. food poisoning, it can be difficult to tell which is causing your stomach to toss and turn. “They can be almost indiscernible,” explains Cory Fisher, DO, a family medicine physician at Cleveland Clinic. But there are some clues that can help you understand what’s behind your gastrointestinal distress.

For starters, food poisoning is much more common than the stomach flu. According to the CDC, foodborne illnesses affect one in six Americans annually—about 48 million people. While there’s some overlap (the stomach flu can be spread through contaminated food), an estimated 19 to 21 million come down with a stomach bug each year. 

Here’s what experts want you to know about how to tell if you have the stomach flu or food poisoning—and what can help get you through it. 

What is the stomach flu?

The “stomach flu” isn’t the flu at all, Dr. Fisher says. “Stomach flu is a lay term that encompasses any viral infection that causes nausea, vomiting, and/or diarrhea,” explains Shira Doron, MD, MPH, Chief Infection Control Officer for Tufts Medicine and Hospital Epidemiologist at Tufts Medical Center. “The medical term is viral gastroenteritis.”

She says the most common cause of viral gastroenteritis is the norovirus—but other viruses can cause the same stomach flu symptoms, too. 

Norovirus is extremely contagious, warns the CDC. It’s most often transmitted by exposure to poop or vomit particles from a person with the virus—but these stomach flu particles spread easily through several different ways:

• Contaminated surfaces: If a person with norovirus touches a surface or object, the virus can survive up to two weeks or longer. 
• Contaminated water: This could result from septic tank leaks or from exposure to water that contains infectious poop or vomit particles. 
• Contaminated food: If a person with norovirus touches food, food is placed on a counter with norovirus particles on it, or food is washed with contaminated water. 

While person-to-person or surface contact are the most common means of transmission, norovirus particles can also stay airborne for up to two hours. A study published in Scientific Reports found that even flushing the toilet can expose someone to the norovirus. 

Many other pathogens can cause the stomach flu as well, including rotavirus and adenovirus. Rotavirus most often affects children (and there’s a vaccine to help protect infants), while norovirus is more common in adults. Adenovirus tends to cause milder illness comparatively. 

Symptoms of the stomach flu

The “stomach flu” is an infection of the gastrointestinal tract that typically lasts between five to seven days, Dr. Fisher says. (Though in milder cases, you may kick the bug in a day or two.) 

The most common symptoms of viral gastroenteritis are vomiting, abdominal discomfort, and diarrhea. However, Dr. Doron adds that it can also cause: 

• Abdominal pain and cramps
• Fever
• Body aches
• Chills
• Headache
• Fatigue 

What is food poisoning?

“Food poisoning is an illness that is acquired from something someone ate or drank,” Dr. Doron says. “The causes are varied and can include viruses, bacteria, parasites, and toxins.” In addition to food harboring infectious particles (like E. coli), food poisoning can also result from spoiled or tainted food, Dr. Fisher adds. 

While norovirus-contaminated food is one type of food poisoning, there are many other possible causes, which is why it’s far more prevalent than the stomach flu. 

According to Johns Hopkins Medicine and the Mayo Clinic, food poisoning can occur due to:

• Undercooked meat, poultry, and eggs: Undercooked food can expose you to bacteria such as salmonella, Bacillus cereus, and campylobacter. Undercooked beef—particularly ground beef—can put you at risk for E. coli as well. 
• Meat, fish, and poultry left at room temperature for too long: Consuming food that’s been left out too long can expose you to multiple types of bacteria, including Clostridium perfringens. This bacteria may also be found in raw meat, poultry, eggs, and even vegetables harvested from contaminated soil. 
• Unpasteurized dairy (especially milk and soft cheeses): These products can expose you to Listeria. This foodborne infection may also be found in deli meats, hot dogs, and raw sprouts. Unpasteurized dairy can contain salmonella, campylobacter, E. coli, and Clostridium perfringens as well.
• Improper food handling: Staphylococcus aureus (a type of staph infection) or foodborne parasites can spread when someone with the bacteria doesn’t wash their hands before handling food. 
• Food washed in dirty or contaminated water: The viral disease hepatitis A can spread through uncooked foods that have been exposed to contaminated water, such as raw produce. Raw or undercooked shellfish can also contain viruses like hepatitis A. 
• Improper food preservation: If foods are not correctly canned/preserved (or there’s damage to the container), botulism bacteria can grow. Botulism is a rare but deadly form of food poisoning. Some expired foods, such as jarred condiments, can be bacterial breeding grounds as well. 
• Shellfish poisoning: Can occur from eating shellfish harvested from coastal seawater that’s contaminated with toxins (even if you cook the shellfish).

Symptoms of food poisoning

The symptoms of food poisoning are very similar to the stomach flu, Dr. Fisher says. “Like with the stomach flu, abdominal pain and cramps, body aches, chills, headache, and fatigue can occur,” explains Dr. Doron. “But depending on the pathogen or toxin causing the food poisoning, additional symptoms are possible, including neurological effects.” 

The cause behind food poisoning also affects the timing and duration of symptoms, says Dr. Doron. However, in most cases, symptoms begin after 24 hours of eating or drinking a contaminated item. 

While less common, some bacteria, pathogens, and viruses can trigger symptoms at different times. For instance, according to the Mayo Clinic:

• Food infected with bacteria like staph or Bacillus cereus can make you start feeling sick within 30 minutes. 
• Other bacteria, such as campylobacter, may take two to five days before you experience symptoms. 
• Some viral foodborne infections, such as hepatitis A, can take 15 to 50 days before illness occurs. 

Key differences: Stomach flu vs. food poisoning

It’s often not possible to tell the difference between the stomach flu and food poisoning, Dr. Doron says. Remember, norovirus (a primary cause of the stomach flu) is a common cause of food poisoning, too—and so the symptoms can be identical. 

“The best clue that you have for food poisoning is that other people you ate with are sick at the same time,” Dr. Doron says. 

Other subtle differences between food poisoning and the stomach flu can be:

• Symptom onset for food poisoning: “It is rare for the symptoms of any type of food poisoning to begin within 24 hours after eating or drinking the contaminated item,” Dr. Doron says. “While people tend to implicate the last thing they ate as the cause of their food poisoning symptoms, that is rarely the case.” Still, food poisoning symptoms tend to come on faster than the stomach flu. 
• Cause and course of the illness: Food poisoning often affects multiple people who ate the same thing. “As opposed to the stomach flu, which is spread from contact to contact over the course of a few days, with a short incubation period in between,” Dr. Fisher explains. “Think: My child was sick three days ago, and now I’m sick.”
• Duration of symptoms: Food poisoning typically resolves faster than the stomach flu, often as quickly as 24 to 48 hours. “The symptoms of nausea, vomiting, abdominal pain, and diarrhea can be exactly the same, but a stomach flu tends to linger a bit longer,” Dr. Fisher says. “Especially the diarrhea, which can last for over a week.” 
• Infection risk: Food poisoning is not contagious. However, the stomach flu is highly transmissible. 

Treatment for stomach flu vs. food poisoning

“Most types of food poisoning resolve on their own without treatment,” Dr. Doron says. The same goes for the stomach flu—you generally just have to wait it out. But in both cases, you can manage symptoms at home for a speedier recovery.

To get over the stomach flu or food poisoning, the main goal is to stay hydrated and allow your body to recover. “Usually clear fluids, rest, and the tincture of time are enough,” Dr. Fisher says. “If you have vomiting and/or diarrhea, it’s important to hydrate even if that means taking tiny sips throughout the day, which might be easier on an upset stomach,” Dr. Doron adds. 

Antidiarrheal medications like Imodium or Pepto-Bismol might also help ease discomfort—and you can take Tylenol or paracetamol for symptoms like fever or body aches. “But severe or prolonged food poisoning symptoms may require a trip to the doctor for a test and appropriate therapy,” Dr. Doron says. 

When to see a doctor

Whether you suspect you have food poisoning or the stomach flu, “You should see a doctor if your symptoms last more than a few days or if you cannot maintain good hydration,” Dr. Fisher says. “Especially if you have both vomiting and diarrhea, which makes it very difficult to keep enough liquids in.” 

Dr. Doron says that signs and symptoms of severe dehydration requiring medical attention include:

• Dizziness
• Confusion
• Fainting
• Muscle cramps
• Rapid heart rate

“If you cannot keep up with hydration and become dehydrated, you may need fluids administered by IV,” she explains. “Sometimes you will get an anti-nausea drug at the same time, which can help you feel better.” Your doctor can also prescribe you nausea or diarrhea medication that’s stronger than what you can get over the counter, Dr. Fisher adds. 

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