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What is gastroenteritis, or 'stomach flu,' and how do you get better?

This very common condition can be caused by viruses, bacteria or parasites.
Marcos Calvo / Getty Images
/ Source: TODAY

When a person feels a “stomach flu” coming on, there’s some misery ahead.

But even though the term covers a host of unpleasant symptoms and the illness can be caused by a virus, there’s actually no influenza involved.

“It has nothing to do with the flu and in fact, (stomach flu) doesn’t have any medical meaning in the medical world,” Dr. Joseph Vinetz, an infectious disease expert and professor at the Yale School of Medicine in New Haven, Connecticut, told TODAY.

The gastrointestinal distress many people are describing is actually gastroenteritis — in its viral form, the second most common illness in the U.S., according to the National Library of Medicine.

Here is what to know about the condition:

What is gastroenteritis?

It’s an inflammation of the stomach and intestines that can be caused by many different viruses (but not flu viruses), bacteria or parasites.

“Everybody gets it. I’ve had it,” Vinetz said, recalling it happened to him during his travels. In those cases, the condition is sometimes called traveler’s diarrhea.

Many people know about the condition in the context of the highly-contagious norovirus, which is often behind outbreaks on cruise ships. A norovirus infection is sometimes also referred to as winter vomiting disease because it can be more persistent at low temperatures.

The virus is “super stable” in the environment and hard to clean, Vinetz noted. You can catch it by consuming contaminated food or drinks, touching a contaminated surface and then putting fingers in your mouth or having direct contact with someone who is infected, according to the Centers for Disease Control and Prevention.

When people think they have the stomach flu or a stomach bug, it’s probably norovirus, the agency added. Outbreaks have been on the rise since January: There were 448 norovirus outbreaks reported to the CDC from August 1, 2021 to March 5, 2022, compared to 78 during the same period during the previous seasonal year. Experts told NBC News the lifting of COVID-19 restrictions may be helping the norovirus spread. 

Bacterial gastroenteritis is less common than the viral kind, with E. coli and salmonella among the culprits. This foodborne illness has been previously linked to outbreaks involving romaine lettuce and bean sprouts, Vinetz said: “You eat it, the bacteria come in, they set up shop and produce these bacterial toxins that cause diarrhea.”

What are the symptoms of gastroenteritis?

The main symptom of gastroenteritis is diarrhea, which may be accompanied by nausea and vomiting. Patients can also experience stomach pain, fever, headache and body aches.

What is the treatment for gastroenteritis?

In most cases, there’s no specific treatment other than supporting the body as it gets through the illness over one or two days. Gastroenteritis usually gets better on its own, Vinetz said.

The main concern is making sure a patient doesn’t get dehydrated. When people have diarrhea, they lose water, sodium and potassium, which can lead to life-threatening alterations in the salts in their blood, he noted.

Patients need more than plain water to replenish the lost minerals. Vinetz recommended a product like Pedialyte because it has a better salt mixture than sports drinks. Chicken soup is also a good option, he added.

When people can’t keep down what they drink, they need intravenous fluids.

If it’s the bacterial form of gastroenteritis and people become seriously ill, get the bacteria in their bloodstream, have an underlying illness or are immunocompromised, antibiotics may be an option, but they’re reserved for very severe cases, Vinetz said.

Could COVID-19 be mistaken for gastroenteritis?

COVID-19 symptoms can include diarrhea, nausea or vomiting. But the illness generally doesn’t come just with gastrointestinal issues — there are usually other symptoms such as a sore throat, stuffy nose or cough, Vinetz noted.

A person can always take an at-home COVID-19 test to make sure.

When to seek help for the 'stomach flu'

Unless somebody is extremely sick or immunocompromised, a day or two of symptoms typically doesn’t require testing or treatment — it’s just watching and waiting, plus plenty of fluids, Vinetz said.

“The general advice is: If you’re not better after a couple of days, go see a doctor,” he noted.

“If you can’t keep anything down or are getting dizzy because you’re getting dehydrated, then you need to see a doctor or go to the emergency room.”

How to prevent a norovirus infection

Wash your hands with soap and water after going to the bathroom and before preparing food. Clean and disinfect surfaces with a solution that contains five to 25 tablespoons of household bleach per gallon of water, the CDC advised.