Norovirus is a common and very contagious virus. It causes nausea, vomiting and diarrhea. Your symptoms may be similar to the stomach flu, but they have a different cause. Norovirus spreads easily through close contact or on contaminated food or surfaces. There isn’t a vaccine for norovirus, but the illness runs its course in fewer than three days.


What is norovirus?

Norovirus is a group of viruses that causes severe vomiting and diarrhea. It’s a very common illness and it’s very contagious. Norovirus outbreaks usually happen seasonally in colder months. The infection is the No. 1 cause of foodborne illness in the United States.

The first norovirus outbreak occurred in Norwalk, Ohio, USA, in a school in 1968. For this reason, the first strain of norovirus was known as the Norwalk virus.

What is the difference between norovirus and the stomach flu?

Norovirus causes gastroenteritis, which some people may call the “stomach flu.” The influenza virus causes respiratory flu, not gastroenteritis.

How many types of norovirus exist?

There are several different types (strains) of norovirus. It’s in the Caliciviridae family of viruses that cause inflammation of your stomach and intestines (gastroenteritis). In this family, there are 10 groups with 48 types. The most common type is GII.4.

How common is norovirus?

Norovirus is very common. Globally, about 685 million cases are reported each year. Of that estimate, over 200 million cases affect children.

Is norovirus seasonal?

Norovirus outbreaks occur most often between November and April in countries above the equator and between April and September in countries below the equator. There’s usually no specific season for outbreaks in areas on the equator.


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Symptoms and Causes

What are the symptoms of norovirus?

Symptoms of norovirus include:

In addition, you may also have:

Symptoms usually appear 12 to 48 hours after exposure to the virus and last one to three days.

Are norovirus symptoms the same in children and adults?

Symptoms of norovirus are usually the same in both children and adults. Adults may experience more diarrhea than children and children may vomit more than adults.

What causes norovirus?

A virus in the Caliciviridae family causes norovirus. This virus, when it enters your body, makes your stomach and intestines swell or become inflamed. This is a condition called gastroenteritis, which leads to symptoms of norovirus.


How do you get norovirus?

You can get the norovirus infection in many ways, including through:

  • Close contact with someone who has the virus.
  • Touching contaminated surfaces and then touching your mouth or nose.
  • Eating or drinking contaminated foods or beverages.

Norovirus is the biggest cause of illness from contaminated food in the U.S. The virus typically spreads when someone who has the virus touches food before serving it to someone else. Sometimes, certain foods, including oysters and other seafood, are naturally contaminated with norovirus.

Is norovirus contagious?

Yes, norovirus is highly contagious, which means it spreads easily. If you have the virus, your body sheds (releases) billions of tiny virus particles that can make others ill, too. It only takes a few particles to make someone else sick.

After you come into contact with norovirus, it can take 12 to 48 hours before you start to show symptoms. This amount of time before you get sick is called an incubation period. After your symptoms stop, you’re still contagious for up to 48 hours.

What are the risk factors for norovirus?

Anyone can get norovirus. You’re more likely to get norovirus if:

  • You come into contact with someone who has the virus.
  • Your genes make you more likely to develop symptoms (genetic susceptibility).

What are the complications of norovirus?

If you have norovirus, you’ll feel very sick. This can cause you to throw up and have diarrhea. When you’re unable to keep nutrients in your body, you’re at risk of dehydration. Symptoms of dehydration include:

  • Peeing less often or having dark-colored pee.
  • Having a dry mouth.
  • Feeling weak or dizzy.
  • A headache.

Children may have the above symptoms, along with:

  • Crying without tears.
  • Fussiness.
  • Sleepiness throughout the day.

Norovirus can make it difficult for you to eat or drink because the inflammation in your intestines and stomach causes you to vomit or have diarrhea. You still need to make an effort to eat and drink. You can do this by eating and drinking more often throughout the day, eating slowly and taking small bites or taking little sips of fluids. If you eat too quickly or too much, your body may reject the food intake.


Diagnosis and Tests

How is norovirus diagnosed?

A healthcare provider will diagnose norovirus after learning about your symptoms. Testing usually isn’t necessary, but a provider may test a stool sample to confirm your diagnosis. Tests are usually necessary if you have an underlying medical condition that affects the performance of your immune system and your ability to fight infections.

Management and Treatment

How is norovirus treated?

There isn’t a cure for norovirus. Treatment for the infection focuses on relieving your symptoms, which will go away in one to three days. You can manage your symptoms by:

  • Drinking plenty of liquids, especially liquids that contain electrolytes.
  • Getting a lot of rest.
  • Eating soft, bland foods.

Is there a vaccine for the norovirus?

No, there isn’t a vaccine available for norovirus yet. Research is ongoing to learn more about how you can protect yourself from the virus.


Can norovirus be prevented?

Some precautions you can take to reduce your risk of getting norovirus include:

  • Washing your hands often with soap and water.
  • Washing your food before eating it (fruits and vegetables).
  • Cooking your food thoroughly (especially seafood or shellfish) or to an appropriate temperature (at least 145 degrees Fahrenheit, or 62.77 degrees Celsius).
  • Avoiding contact with people who have a norovirus infection.
  • Cleaning and sanitizing frequently touched surfaces and objects.
  • Washing your clothes thoroughly, especially if they’re soiled.

Using hand sanitizer doesn’t kill norovirus particles as effectively as washing your hands with soap and warm water. If you have a norovirus infection, you shouldn’t prepare food or take care of others, as you’re at risk of spreading the infection.

Can you get norovirus twice?

Yes, you can get norovirus more than once. There are several types of noroviruses. Your body may build a small immunity (protection from the virus) to the initial type of norovirus, but not all types. This means you can get sick with norovirus multiple times throughout your life. If you do have an immunity to a type of norovirus, it may not last forever. This means that there could be a large gap of time between your first and second infections.

Outlook / Prognosis

What can I expect if I have norovirus?

Norovirus symptoms are usually sudden and harsh. You’ll likely be throwing up (vomiting) or having diarrhea for a few days until the infection runs its course. The thought of eating or drinking can be nauseating. But you’ll put yourself at risk of dehydration if you don’t eat or drink. If you’re unable to eat or drink, contact a healthcare provider.

There are several strains of norovirus, so if you get sick once, it’s likely you can get sick again, as your body hasn’t built an immunity to every type of norovirus. The illness is temporary and doesn’t usually cause any long-term effects.

How long does norovirus stay in my system?

When norovirus enters your body, it’s present in your stool (poop) before you experience symptoms. It can also stay in your system for up to two weeks after your symptoms go away. You’re only contagious after you become infected until 48 hours after your symptoms stop.

Living With

When should I see a healthcare provider?

Visit a healthcare provider if you’re unable to eat or drink. This can lead to dehydration. You should also contact your provider if you have symptoms that last longer than three days.

What questions should I ask my doctor?

  • Do I have norovirus or another type of infection?
  • How do I eat or drink when I’m sick?
  • Can I take any medications to help me feel better?
  • How do I prevent my family from getting sick?

Additional Common Questions

What is the difference between norovirus and rotavirus?

Both norovirus and rotavirus are infections that cause inflammation of your stomach and intestines (gastroenteritis), but they’re different conditions.

Caused by a strain of Caliciviridae.
Caused by a strain of Reoviridae.
Infection lasts between one and three days.
Infection lasts between three and eight days.
Affects anyone at any age.
Affects mostly children and sometimes adults.
There isn’t a vaccine available.
There’s a vaccine available.

A note from Cleveland Clinic

Norovirus is a sudden and frustrating virus. You need to eat and drink, but your body has trouble keeping it down. Luckily, the condition only lasts for a few days. You can try to eat and drink small bites or sips frequently throughout the day instead of eating large meals. Contact your healthcare provider if you can’t eat or if your symptoms last longer than three days. Make sure you wash your hands often with soap and water to prevent the spread of the infection.

Medically Reviewed

Last reviewed by a Cleveland Clinic medical professional on 02/03/2023.

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