Stomach bug or food poisoning? Here's how to tell

Understand the difference between the "stomach flu" and food poisoning, and why prompt treatment is important.

Young woman holding her hands over her stomach

Plagued with nausea, vomiting, abdominal pain and diarrhea? There could be several conditions causing your discomfort, such as a bug you caught from your coworker or ingested at your favorite seafood joint. Illnesses like food poisoning and gastroenteritis (often erroneously labeled “stomach flu”) typically cause little more than temporary pain and discomfort. But being able to identify the cause of your sickness can be helpful, should your condition turn serious.

Hugh Bonner, MD, a family practitioner with Saint Francis Healthcare in Wilmington, Delaware and family practitioner Timothy O'Neill, MD with Saint Joseph Mercy Health System in Pontiac, Michigan have both treated their share of patients with gastrointestinal distress. Here's what they want you to know about identifying—and treating—stomach bugs. 

Signs you have the stomach flu

"The stomach flu is a misnomer for a group of viruses or bacteria that can cause gastrointestinal symptoms like nausea, vomiting or diarrhea," Dr. Bonner says.

Despite the similarity in the name, the stomach flu (a.k.a. gastroenteritis) is a different bug entirely from influenza, a respiratory sickness that can cause a sore throat, cough, fever, aches and runny or stuffy nose. Influenza may also cause vomiting and diarrhea, although those symptoms are uncommon and occur more frequently in children than adults.

The stomach flu can also result in head and muscle aches and a low-grade fever. In most cases, symptoms last for a day or two, but can linger for a week or more.

The stomach bug is caused by viruses, bacteria or parasites that spread through contact with a sick person. Norovirus and rotavirus are among the most common germs that cause gastroenteritis and are most likely to spread when people are in close contact, such as among children in daycare, people in hospitals and nursing homes, military personnel in confined quarters, students in dormitories and those traveling on cruise ships. Anyone, though, can be infected.

People with compromised immune systems—such as those with HIV or AIDS—and those undergoing chemotherapy are at a higher risk for coming down with severe symptoms and potentially dangerous complications.

Treating gastroenteritis

Your body loses fluids and electrolytes when you're sick, so replacing them is important, says Bonner. Drink plenty of water and try easing back into eating by first munching bland foods like saltine crackers, toast, rice or bananas or sipping low-sodium broth, all of which can help replace some of the nutrients your body may have lost. Skip dairy, caffeine and fatty eats like beef and set food aside if you begin to feel queasy. Symptoms like diarrhea can also be treated with over-the-counter medications, but always consult your doctor first.

Most cases of gastroenteritis do not require medical attention, Dr. O'Neill says, but if you can't keep solid food or fluids down or if your symptoms worsen, those are signs you should see a doctor.

Dehydration is one of the most common complications associated with gastroenteritis and it can be dangerous if left untreated. If you become extremely thirsty, notice your urine is darker than usual or you develop dry skin and mouth, see your doctor. If need be, a medical professional can administer fluids and electrolytes intravenously to treat severe cases of dehydration.

A decrease in the volume of blood in the body, known as hypovolemia, is a medical emergency that can result from extreme dehydration stemming from excessive vomiting or diarrhea. Clammy skin, confusion, sweating, rapid breathing and loss of consciousness are also signs of this complication of extreme dehydration and should be assessed by a medical professional without delay.

Although severe gastroenteritis isn't common, it is responsible for an estimated 10,000 deaths in the United States each year. Clostridium difficile, a bacterium that can lead to serious inflammation of the colon, is responsible for a majority of these deaths; norovirus contributes to fewer cases.

Antibiotics don’t treat the kind of gastroenteritis caused by a virus. And while they are rarely used to treat bacteria-based gastroenteritis, antibiotics may be given to people with weakened immune systems or those with severe diarrhea.

To help determine the cause of your ailment and the best course of treatment, your physician may ask about your medical history and the onset and severity of your symptoms. A fever and bloody stool, for example, may be signs of a bacterial or parasitic infection. A stool culture may also be performed to identity the specific bacteria that may be causing your symptoms.

When bacteria in food is to blame

"Food poisoning and gastroenteritis differ, but it can be tough to tell the two apart," O'Neill says. The diseases' symptoms—nausea, vomiting, stomach cramps and diarrhea—are similar. Signs of food poisoning—also known as foodborne illness—can develop hours or even days after eating contaminated food and can range from mild discomfort to severe pain and sickness.

An estimated 9.4 million illnesses are linked to foodborne contaminants in the U.S. each year. Bacteria are the most common cause of food poisoning, according to O'Neill, but viruses and parasites can cause sickness, too. Among the most prevalent foodborne bacteria are Salmonella, E.coli and Listeria, which often lurk in raw or undercooked meat and poultry, seafood and shellfish, unpasteurized dairy, eggs, deli meats and fresh produce. Norovirus can also be contracted through contaminated food.

Between 2009 and 2015, there were nearly 2,953 outbreaks with a single confirmed cause in the U.S., according to the Foodborne Disease Outbreak Surveillance System. Norovirus was responsible for 38 percent of illnesses and Salmonella was the cause of 30 percent of outbreak-related sickness. Salmonella, E.coli and Listeria were linked to more than 80 percent of hospitalizations and deaths during the six-year period.

Like stomach flu, most cases of food poisoning will subside within a few days without any medical treatment. Symptoms can come and go within eight to 12 hours, O'Neill says. While you’re in the throes of stomach distress, staying hydrated with clear liquids is key. Nausea and diarrhea can also be managed with over-the-counter medications, but you should consult your healthcare provider before taking any drugs or supplements.

If you develop symptoms like a fever, severe abdominal pain or bloody diarrhea, seek prompt medical attention, says O'Neill. Persistent vomiting and signs of dehydration should also be checked by a doctor, Bonner says.

"Foodborne illnesses can be pretty serious, even fatal in some circumstances, so we try to figure out where they came from," O'Neill says. To help your physician ascertain the cause of your illness, you'll likely be asked to provide a detailed account of your symptoms, and you may be given a physical exam and asked to provide a stool sample.

Your healthcare provider can treat severe symptoms with fluids and electrolytes, and you may be prescribed antibiotics in some cases to help the body fight certain bacteria. Most people who contract food poisoning make a full recovery, but there is a risk for complications, especially among those most vulnerable, including infants, pregnant women and older adults.

Pregnant women who become infected with Listeria are at an increased risk for stillbirth and premature delivery. E.coli can damage the lining of blood vessels in the kidneys, which can lead to kidney damage. Salmonella, meanwhile, can lead to inflammation of brain and spinal cord tissue (meningitis), which can be fatal.

Keep yourself healthy

Avoiding foodborne illnesses and the stomach flu entirely is difficult, but there are some safeguards you can deploy.

Washing hands effectively and frequently helps prevent the spread of germs, Bonner says. Vaccinating children against rotavirus—the inoculation is given to infants younger than 8 months of age—can help prevent infection, as can staying away from anyone with the stomach flu. Disinfecting commonly-touched surfaces like doorknobs and faucets can also help reduce the risk of contraction.   

Food poisoning can be prevented by storing, washing and preparing food properly:

  • Perishable foods, including raw meat, should be frozen or refrigerated and kept at room temperature for no more than two hours.
  • Poultry should be cooked until the internal temperature reaches at least 165 degrees Fahrenheit. Ground beef and lamb should be cooked to at least 160 degrees and roasts, steaks and chops to at least 145 degrees. 
  • Give fruits and vegetables a thorough wash in fresh, running water.
  • Wash hands for at least 20 seconds with soap and warm water after handling raw meat, fish or eggs, using the bathroom or changing a diaper.

"It's also never a bad idea to pay attention to recalls and outbreak news," O'Neill says. The Centers for Disease Control and Prevention and the U.S. Food and Drug Administration provide summaries so you can follow the latest updates.

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