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The Truth About Stomach Flu

It’s not really the flu, but gastroenteritis.
WebMD Feature

No doubt you've heard people complain they have "stomach flu." You may have complained about it yourself after a bout of nausea, vomiting, and diarrhea that seems to come from nowhere. In fact, though, stomach flu is a misnomer. There’s no such thing.

The flu, influenza, is a respiratory infection that affects the lungs. But when people say stomach flu, they usually mean vomiting or diarrhea, says Jay Solnick, MD, professor of medicine and an infectious disease specialist at the University of California at Davis School of Medicine. "Stomach flu is a vague, fuzzy way to describe these things," he says.

Doctors prefer the term gastroenteritis, which means irritated and inflamed stomach and intestines (the gastrointestinal tract) and may be any number of things, including bacteria or viruses.

Here, Solnick and other experts tell WebMD more about gastroenteritis, what causes it, what symptoms to expect, what self-treatment works, and when to seek medical help.

What Is Gastroenteritis?

The term gastroenteritis is broad even when used by doctors, Solnick says. "If I was talking to a colleague and told him a patient of mine had gastroenteritis, my colleague would expect that I meant he had nausea or vomiting or diarrhea," he says.

Generally, however, doctors use the term gastroenteritis to describe the sudden onset of nausea, vomiting, and diarrhea, says David Burkhart, MD, a staff physician at the Indiana University Health Center in Bloomington.

Usually, gastroenteritis is caused by bacteria, viruses, or parasites, which can spread quickly through contaminated food or water.

  • Bacteria that cause gastroenteritis include Escherichia coli. Salmonella, Campylobacter, and Shigella. These bacteria are usually found in food, but can be spread person to person, Burkhart says.
  • Viruses that trigger gastroenteritis include adenoviruses, rotaviruses, calciviruses, astroviruses, and norovirus. Certain viruses are found in specific places, Burkhart says. For instance, norovirus often shows up on college campuses, lingering on doorknobs and shared keyboards, spreading the gastroenteritis among students.
  • Parasites and protozoans that commonly lead to gastroenteritis include Giardia and cryptosporidium. The parasite Giardia lives in the intestines of infected people or animals, and often spreads when someone swallows polluted water.
  • Chemical toxins in seafood can also cause gastroenteritis. So can exposure to heavy metals, such as lead in drinking water.

Other causes of non contagious gastroenteritis include food allergies, caffeine, or medications such as antibiotics, steroids, aspirin, and laxatives.

Gastroenteritis Symptoms

Besides the nausea, vomiting, and diarrhea, symptoms of gastroenteritis can include a low-grade fever of about 99 degrees.

The diarrhea is typically mild to moderate: two to four loose stools a day for teens and adults. For babies, it typically means the stools seep through the diapers. Many people also complain of painful bloating.

More serious symptoms include:

  • Vomit or stool that contains blood
  • Long-duration vomiting, such as more than 48 hours
  • Fever that is 101 degrees F. or higher
  • Abdominal swelling or pain in the right lower side of the abdomen
  • Dehydration


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