How Long Does the Stomach Flu Last?

A Flu Shot Won't Help

"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 the viruses that cause viral gastroenteritis, which is characterized by inflammation of the stomach and intestines, per the CDC.

Some symptoms overlap between the flu and norovirus, like body aches, nausea, and low-grade fever, said Gary Rogg, MD, an internist affiliated with Westchester Medical Center in Valhalla, New York.

But a flu shot won't protect against noroviruses, and there's no such thing as a norovirus shot, at least not for adults (there is a vaccine for the rotavirus, a type of stomach flu that affects infants and young children, according to the CDC) .

What Does Norovirus Have To Do With the Stomach Flu?

The norovirus family of viruses is most often to blame for adult viral gastroenteritis, although there are other troublemakers, including adenovirus, astrovirus, and rotavirus, according to the CDC.

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.

Is Norovirus Contagious?

Yes, norovirus is extremely contagious. It spreads via the fecal-oral route, which basically means germs 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.

Be especially diligent 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, advised Ryan Madanick, MD, a gastroenterologist and assistant professor of medicine at the University of North Carolina School of Medicine in Chapel Hill, North Carolina.

Can You Get Norovirus From Food?

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. It can be confusing to know which is which, as the CDC says that food poisoning can come on come on quickly within hours after eating contaminated food, but it can also take days to weeks, depending on what type of germ was ingested. The incubation period for norovirus is typically 12-48 hours after being exposed to the virus.

However, norovirus is the number-one cause of foodborne illness in the US, causing 58% of foodborne illnesses in the US each year, according to the CDC. You can get viral gastroenteritis from sewage-contaminated food—like leafy greens, fresh fruits, and shellfish—or water, or from meals prepared or handled by an infected person (hence, all those "wash your hands" signs in restaurant bathrooms).

How Can You Prevent Norovirus?

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, and wash laundry carefully, using gloves to handle soiled clothing and bedding if you can (be sure to properly remove your gloves according to CDC guidelines).

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), per the CDC or another disinfectant approved by the Environmental Protection Agency (EPA) as effective against norovirus.

What Are the Symptoms of Norovirus?

Common stomach flu symptoms are diarrhea, fever, nausea, vomiting, stomach or intestinal cramps, headaches, and body aches, per the CDC. They might not hit you immediately after you're infected with a gastrointestinal virus, but typically develop gradually, over one or two days, explained Dr. Madanick.

How Long Does Norovirus Last?

According to the CDC, norovirus is "self-limiting," meaning it resolves on its own and rarely requires medical treatment.

If you've got viral gastroenteritis, you should start to feel better within 1-3 days, per the CDC. If, however, you don't feel better in that time and diarrhea or vomiting continue for more than three days—or you have symptoms of dehydration—call your healthcare provider, as it could mean you have something more serious.

Is Dehydration a Risk?

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.

Sports drinks may help replenish the electrolytes, but the CDC more highly recommends pediatric electrolyte solutions as a better choice to replace lost electrolytes, nutrients, and minerals due to vomiting and diarrhea (or simply not staying hydrated, even when you're not sick).

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 MedlinePlus, a resource of the National Library of Medicine.

If you think you, your child, or someone you are looking after is severely dehydrated, get emergency help right away.

How Much Water Should I Drink?

Try to avoid drinking too much plain water or beverages like soda or juice that contain sugar but not enough of the right electrolytes, said Dr. Rogg. "The biggest mistake that people make [when they have a norovirus infection] is just trying to drink a lot of water," added Dr. Rogg. "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, explained Dr. Rogg. And taking in sugar without salt can make your diarrhea worse. You also want to avoid fluids containing caffeine or alcohol.

The CDC says that oral rehydration fluids that you can get over the counter are the recommended way to replace electrolytes, as well as the nutrients and minerals you lose with vomiting and diarrhea (although water and sports drinks will help in a pinch).

Are There Any Treatments for Norovirus?

There is no treatment for viral gastroenteritis, besides time and symptom relief. Antibiotics won't work on a virus, so don't be surprised if your doctor doesn't offer them.

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 healthcare providers don't usually recommend them if you have bloody diarrhea or a high fever, so be sure to check in with your healthcare provider before taking them.

When Should I Call My Healthcare Provider?

Diarrhea and vomiting on their own are probably not cause for alarm, but if you see blood in your stool or vomit, call your healthcare provider right away, per the CDC. 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.

The CDC also recommends seeking 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 102 degrees Fahrenheit.

Who's at the Greatest Risk of Contracting Norovirus?

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, said Dr. Rogg.

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.

What Else Should I Know About Norovirus?

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, warned Dr. Rogg. "Don't eat as if you were well until you've felt fine for a couple of days. 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," advised Dr. Rogg. 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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