Is the Stomach Flu Contagious? 14 Questions You Have About Norovirus, Answered

Despite the fact that it’s so common, many people don’t know much about the stomach flu. That’s possibly because it has many other names, including stomach bug and viral gastroenteritis (its official name). It may also be referred to as rotavirus or norovirus, as they’re the two main types of viruses that cause it. 

Confusingly, it’s not anything to do with the flu, which is caused by the influenza virus. But it can definitely be just as bad. First off, there’s vomiting and diarrhea, and don't even get us started on the cramps. If you’ve been there, you won’t forget it in a hurry.  

Here are 13 things you need to know about viral gastroenteritis (its true medical name), including how long the stomach "flu" lasts in adults.

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Um, no. It has nothing to do with the flu, remember?

“The flu” is influenza, a virus that circulates the globe each year attacking the nose and throat as it spreads through communities in waves. Flu shots protect against that virus—but not ones that cause viral gastroenteritis, which is characterized by inflammation of the stomach and intestines, per the Centers for Disease Control and Prevention. 

If you’re confused, you’re not the only one. Some symptoms overlap, like body aches, nausea, and low-grade fever, says Gary Rogg, MD, an internist at Montefiore Medical Center in New York City.

But a flu shot definitely won't protect against stomach bugs. There's no such thing as a stomach flu shot, at least not for grown-ups.

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Now that we’ve moved on from the flu, let’s tackle the real culprit: norovirus.

This family of viruses is most often to blame for adult gastroenteritis, although other troublemakers include adenovirus and astrovirus, and rotavirus is the most common cause of viral gastroenteritis in babies and young children.

Norovirus can spread like wildfire in any crowded place, causing outbreaks in daycare centers, schools, cruise ships, hospitals, and nursing homes—basically, any place people come into contact with each other. According to the CDC, norovirus is the leading cause of acute gastroenteritis among people of all ages in the United States, causing an estimated 19 to 21 million cases each year.

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Yes, extremely. It spreads via the “fecal-oral route” (yep, that’s just as gross as it sounds), which basically means viruses from infected feces or vomit find their way into our mouths. The CDC says people with norovirus illness can shed billions of norovirus particles, and you only need a few of them to get sick. Very diligent hand washing is your best defense, according to Dr. Rogg.

Wash carefully if you're changing diapers or cleaning up after a sick child, and grown-ups in the household should clean up after themselves if they can, advises Ryan Madanick, MD, a gastroenterologist and assistant professor of medicine at the University of North Carolina School of Medicine in Chapel Hill, North Carolina.

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Viral gastroenteritis isn't the same thing as food poisoning, which refers to any illness caused by food contaminants, including dangerous toxin-producing bacteria like salmonella. While food poisoning tends to come on quickly, typically 2-6 hours after eating contaminated food, the incubation period for stomach flu is a lot longer: 24-48 hours after being exposed to the virus. 

However, norovirus is the number-one cause of foodborne illness in the US, per the CDC. You can get viral gastroenteritis from sewage-contaminated food or water, or from meals prepared or handled by an infected person. (Hence all those "wash your hands" signs in restaurant bathrooms.)

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Compared to other viruses, noroviruses can be surprisingly hardy and live for days on household surfaces, which is why they spread easily. (That, and the fact that very few virus particles are needed to cause an infection.)

Wash your hands with soap and water, which is more effective than hand sanitizers, per the CDC. Avoid food prep if you're sick (you can still be infectious for 3 days or more after symptoms wane), and wash laundry carefully, using gloves to handle soiled clothing and bedding if you can.

When cleaning hard surfaces, use a chlorine bleach solution with a concentration of 1000 to 5000 ppm (5 to 25 tablespoons of household bleach per gallon of water) or another disinfectant approved by the Environmental Protection Agency (EPA) as effective against norovirus.

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Common stomach flu symptoms are diarrhea or constipation, fever, nausea and/or vomiting, stomach or intestinal cramps, joint stiffness, and weight loss (unsurprising, considering all that diarrhea and vomiting). They might not hit you immediately after you're infected with a gastrointestinal virus, but typically develop gradually, over one or two days, Dr. Madanick explains.

On the other hand, food poisoning tends to strike fast and hard—within a few hours after you're exposed to the offending substance—and symptoms tend to be more dramatic, such as explosive vomiting and diarrhea.

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Both stomach flu and other types of food poisoning are what doctors call "self-limiting," meaning they play themselves out and rarely require medical treatment.

While norovirus is the leading cause of foodborne illness, other bugs like salmonella are more likely to result in hospitalization.

If you've got viral gastroenteritis, you should start to feel better after two or three days. While food poisoning due to other causes hits you harder and faster, it goes away faster too; you may be back to normal in a day or two.

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Absolutely. It stands to reason that if you're losing lots of fluid through watery diarrhea and vomiting, you need to replace that fluid. But remember that you're also losing sodium, potassium, and other minerals (known as electrolytes), and they need to be replaced, too.

You should drink Pedialyte, or similar oral electrolyte solutions that contain salts and sugar as well as water, if you have severe diarrhea. Sports drinks aren't a great choice, because the mix of salts and sugars they contain isn't exactly right in terms of replacing fluid lost to diarrhea and vomiting.

If you don’t take steps to treat dehydration, it can lead to serious problems, and in really severe cases, require hospitalization for intravenous treatment, warns the CDC. Dehydration can be particularly serious in kids, so be on the look out for this in children with stomach flu. If they’re dehydrated, they might cry with few or no tears, have sunken eyes, and be unusually drowsy, sleepy, or irritable, per the National Institutes of Health. 

If you think you, your child, or someone you are looking after is severely dehydrated, get straight on the phone to the doctor.

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Try to avoid drinking too much plain water, or beverages like soda or juice that contain sugar but not enough of the right electrolytes, says Dr. Rogg. "The biggest mistake that people make [when they have stomach flu] is just trying to drink a lot of water," he adds. "They understand that they have to prevent themselves from getting dehydrated, but what they're actually doing is wrong."

Putting water into your body without adding electrolytes will dilute the electrolytes that still remain in your body, Dr. Rogg explains, and taking in sugar without salt can make your diarrhea worse.

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There is no treatment for viral gastroenteritis, besides time and symptom relief. (Antibiotics won't work, so don't be surprised if your doctor won't give you any.)

Over-the-counter remedies that contain bismuth subsalicylate (like Pepto-Bismol) may help for simple diarrhea, says the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). Antidiarrheal medications may also help ease cramps, but you should avoid them if you have bloody diarrhea or a high fever, as it can make the illness worse.

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Diarrhea and vomiting on their own are not cause for alarm, but if you see blood in your stool or vomit, call your doctor right away. You should also seek help if you experience extreme lethargy, confusion, or an otherwise altered mental state, or a lack of urine (or dark and concentrated urine), which are signs of serious dehydration.

Also get treatment if your symptoms aren't getting better after three days, you have prolonged vomiting that prevents you from drinking liquids, or your temperature spikes above 101.5 degrees Fahrenheit.

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Young children's developing immune systems make it harder for them to fight off viral infections, while their smaller bodies are also at greater risk of becoming dehydrated. Elderly people are also more prone to coming down with viral gastroenteritis and take longer to recover afterwards, Dr. Rogg says.

Anyone with a chronic illness, such as heart disease, asthma, cancer, or kidney disease, or who has HIV or is taking medications that suppress the immune system, should see a doctor if they come down with the stomach flu.

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When you stop vomiting and your diarrhea subsides, you're probably going to feel pretty hungry. But wait a few days before you celebrate with a feast, Dr. Rogg warns. "Don't eat as if you were well until you've felt fine for a couple of days," he advises. "Eat smaller meals, and drink in smaller volumes. Basically, you'll want to avoid eating or drinking in a way that will distend the stomach." Overloading the stomach too soon may make you feel sick all over again, so skip fatty foods and stick to light, easy-to-digest meals.

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