What is norovirus?

Norovirus is a stomach and intestinal virus that’s very contagious. It passes easily through direct or indirect contact with an infected person. It can spread quickly in close quarters such as hospitals, schools, and day care centers.

Most people have some experience with norovirus. It’s a common illness of the stomach and intestinal tract. Norovirus can also be a source of food poisoning, because you can get it from eating contaminated food. The results are the same no matter how you get it.

The hallmark symptoms of norovirus are vomiting and watery, non-bloody diarrhea. These symptoms usually start within 12 to 48 hours of being exposed and can last up to three days. Most people make a full recovery.

There’s no specific treatment except to rest and rehydrate. The most significant complication is dehydration. Norovirus can be serious and even fatal in the very young, older adults, and people with other health problems.

Because there are many norovirus strains, having it once doesn’t prevent you from getting it again. You can lower the risk of disease transmission by washing your hands thoroughly and frequently.

Norovirus is thought to be the most common cause of acute gastroenteritis in the world, leading to 685 million cases a year. Gastroenteritis is inflammation and infection of the stomach and intestinal tract caused by any infectious organism, like bacteria and viruses. Norovirus is responsible for up to 21 million illnesses in the United States each year.

Norovirus symptoms

Symptoms of infection usually start somewhere between 12 and 48 hours after you’ve been exposed to the virus. They can range from quite mild to severe. Some signs and symptoms of norovirus are:

Symptoms usually last between 24 to 72 hours. See your doctor if symptoms persist beyond that or if you see blood in your stools. Severe diarrhea can lead to dehydration, which should be considered a medical emergency. Signs and symptoms of dehydration include:

  • dry mouth and throat
  • decreased output of urine or dark urine
  • no wet diaper for 6 to 8 hours in infants
  • no urine in 12 hours for children
  • sunken eyes
  • sleepiness and fatigue
  • headache
  • dizziness
  • confusion and lethargy
  • rapid heart rate

If your child cries without producing tears, that’s a common sign of significant dehydration. Seek medical care right away. They might also act fussy and irritable.

Dehydration can be life-threatening, especially for the following groups:

  • people with a weakened immune system
  • people with preexisting health conditions
  • the very old and the very young
  • organ or stem cell transplant recipients

It’s estimated that in some cases, about 30 percent of the time, the virus causes no symptoms at all. This is especially common in children.

Learn more about nausea and vomiting: Causes, treatment, and complications »

Norovirus treatment

There’s no special medicine for norovirus. It’s not a bacterial infection, so antibiotics won’t help. Treatment is mainly supportive, with a goal of preventing dehydration. Here are some self-care tips:

Rest

Don’t push yourself. Stay home and rest.

Replenish fluids

Drink plenty of fluids. To replace electrolytes, oral hydration solutions, like Pedialyte, are recommended for all ages. They’re especially necessary in infants and children.

Sports drinks, popsicles, and broths should only be taken by older children and adults. Stay away from sugary drinks, as these can worsen diarrhea. You should also avoid drinks that contain caffeine or alcohol.

Continue your diet

Infants should continue breastfeeding or formula feeding while being rehydrated.

For children and adults, as appetite picks up, some good choices are:

  • soups
  • plain noodles
  • rice
  • pasta
  • eggs
  • potatoes
  • crackers or bread
  • fresh fruit
  • yogurt
  • Jell-O
  • cooked vegetables
  • lean proteins like chicken and fish

Talk to your doctor

You can try an over-the-counter (OTC) anti-diarrheal, but not if you have a fever, severe diarrhea, or bloody stools. Don’t give OTC medications to infants or children with vomiting or diarrhea, unless instructed by your doctor. You should start to feel better within a few days.

However, call your doctor:

  • if you have a fever
  • if you can’t tolerate liquids
  • if your diarrhea is severe or lasts more than three days
  • if your stools are bloody
  • if you have any serious preexisting health problem
  • if you normally take prescription medications, but can’t keep them down

Diarrhea lasting more than three days can lead to severe complications from dehydration. You may require hospitalization to receive intravenous fluids.

Learn more about dehydration: Risks, treatment, and prevention »

Norovirus incubation period

The moment you come into contact with a norovirus, you probably won’t know it. You can pick it up from touching a contaminated surface or from something you eat. You can also get it from person-to-person contact. Once it’s on your hands, you can easily transfer it to your mouth.

The average time between initial contact and first symptoms, or the incubation period, is about 12 to 48 hours, with a median time of 33 hours.

Your first clue that something is wrong may be nausea. Sudden vomiting, abdominal cramping, and watery diarrhea can follow.

If necessary, the virus can be identified in a sample of your stool if done within 48 to 72 hours after symptoms start. In some cases, norovirus can be detected in stool for up to 14 days or even longer.

As long as you’re still shedding the virus in your stool, you can pass it on to others. That’s easy to do because it only takes a small amount of the virus to cause illness. You can spread the infection to others even if you don’t have symptoms.

Keep reading: Am I contagious? When to stay home sick »

How contagious is norovirus?

Norovirus is extremely contagious. Anyone can acquire the virus, and that doesn’t protect you from getting infected by it again. Here’s why it’s so contagious:

  • It takes only 18 virus particles to make you sick.
  • The virus has a short incubation period. That means you can spread it around before you know you’re sick.
  • The virus is hardy and can survive outside your body for several days.
  • You can continue to spread the virus for two weeks or longer after symptoms fade.
  • You can have the virus, but not have any symptoms. Even so, you’re still capable of spreading it around.

A few things can increase your risk of getting the infection, such as:

  • Spending time in a hospital, nursing home, school, or day care center. The virus spreads particularly fast in close quarters. For this reason, your risk may also be higher on a cruise ship, hotel, or in a resort setting.
  • Contact with an infected person, especially if you’re caring for a sick person and are exposed to their vomit or stool.
  • Sharing food, drinks, plates, cups, or utensils with an infected person.
  • Eating food or drinks prepared in unsanitary conditions.

In the United States, most outbreaks occur between November and April.

Read more: How to handle school sick days »

Norovirus in babies

Babies and toddlers are particularly vulnerable to norovirus infection. They’re more likely than healthy adults to have serious complications.

Symptoms in infants and children are likely to include:

  • irritability or fussiness
  • sleepiness
  • vomiting
  • diarrhea

There’s serious risk of dehydration due to vomiting and diarrhea. The younger the child, the less vomiting and diarrhea they can tolerate. Call your pediatrician if your child:

  • is under 6 months old and has experienced vomiting or diarrhea
  • has had six or more watery stools in 24 hours
  • has vomited three times or more in 24 hours
  • has pale or mottled skin
  • isn’t producing tears
  • has sunken eyes
  • has a fever
  • is lethargic or less responsive than usual
  • has bloody diarrhea
  • complains of dizziness
  • produces little to no urine — no wet diapers for an infant in 6 to 8 hours or no urine for 12 hours in an older child
  • has had symptoms lasting two days
  • has a coexisting health problem

Worldwide, about 200 million cases of norovirus a year occur in children under age 5.

It’s estimated that over one million medical visits for U.S. children are due to norovirus. In the U.S., 1 in 278 children will need hospital care for norovirus by their fifth birthday. Of these 1 in 14 will need emergency room care, and 1 in 6 will need outpatient care.

Norovirus spreads quickly among children. Infected children shouldn’t attend school, day care, or other activities. Children should be taught to wash their hands frequently, especially after using the bathroom.

Norovirus prevention

Norovirus is highly contagious and persistent. There’s no vaccine to prevent it, but there are some things you can do to lower the risk of transmission.

  • Wash your hands after using the toilet, changing a diaper, or caring for a sick person. Use soap and running water for at least 20 seconds. If you don’t have access to soap and water, use an alcohol-based hand sanitizer.
  • When caring for a sick person, wear gloves and use plastic bags to dispose of soiled materials or diapers. Use disinfectant or a chlorine bleach solution on contaminated surfaces. Handle contaminated clothes carefully and launder them right away.
  • Don’t consume food or beverages prepared by a sick person.
  • Wash your hands before preparing or eating food.
  • Wash all produce before cutting into or eating it.
  • Don’t eat raw or undercooked seafood.
  • If you’re sick, stay home. This is especially important if you work in food service, healthcare, or education. Sick children shouldn’t attend school, day care, or other activities.
  • Put off travel plans until you’re fully recovered.
  • Don’t use public swimming pools when you have diarrhea.

Remember, you can still spread the virus for up to two weeks after symptoms subside. Because there are many different strains of the virus, having it once doesn’t protect you from getting it again.

Read more: 7 ways to flu-proof your home »

Norovirus transmission

Noroviruses are estimated to cause 60 percent of all cases of acute gastroenteritis from known pathogens. Pathogens are anything that can cause illness, like bacteria or viruses.

Transmission is easy because it takes just a small amount of the virus to cause an infection.

With a short incubation period, you can be spreading it before you even know you’re ill. And you can be contagious for a few days to a few months after symptoms go away. If you have other health problems, you can be contagious even longer.

The pathogens can endure extreme heat and cold and can live outside the body for several days.

The primary way norovirus spreads is the fecal-oral route, but it can also spread through droplets of vomit. This can occur after person-to-person contact, such as when you shake hands. If you don’t thoroughly wash your hands, one touch to your mouth is all it takes. It can spread rapidly in a healthcare setting.

Transmission can also occur indirectly, such as when food, water, or surfaces become contaminated. Just touching an infected doorknob or cellphone could start the chain reaction. When someone vomits, the virus can become airborne, so if it gets in your mouth, it can end up in your intestinal tract.

Norovirus spreads easily in large groups of people.

Norovirus during pregnancy

Getting norovirus when you’re pregnant shouldn’t harm your baby or your own health in the long term.

If you have diarrhea and vomiting while pregnant, it’s a good idea to contact your doctor right away. It may be a case of norovirus, but it could be something else.

Take steps to avoid dehydration, which can be a serious complication of norovirus. When you have vomiting and diarrhea, drink plenty of fluids, like Pedialyte, but limit beverages containing caffeine.

Ask your doctor before taking any OTC medicine during pregnancy.

Contact your doctor if you have signs of dehydration, such as:

  • dark-colored urine
  • decreased urination
  • dry mouth and throat
  • lightheadedness, dizziness
  • loss of appetite
  • fatigue
  • rapid heartbeat
  • headache

Remedies for diarrhea during pregnancy »

Norovirus causes

It all starts when you come into contact with the virus. It could be lurking on your food. Or perhaps you touch an infected light switch or hold someone’s hand before touching your mouth or nose. That’s when those tiny particles gain entry to your body.

You’re unaware as the particles make their way down your esophagus. They pass through your stomach and enter your intestines. The intestines are the norovirus sweet spot, where rapid reproduction seems to take place. Meanwhile, your immune system is alerted to the presence of foreign invaders. It directs an army of antibodies to destroy them.

Most of the time, your antibodies will claim victory over the virus within one to three days. But your body can continue to shed the virus for up to two weeks or longer.

Keep reading: Causes of viral gastroenteritis »

Norovirus with a rash

Rash isn’t normally a symptom of norovirus.

In some cases, the virus can trigger hives (urticaria). It can start out with itchiness and quickly morph into red welts. You know it’s hives when you press on the bump and its center turns white. Hives can be treated with antihistamines. You can also use a cold compress to temporarily relieve itching.

Infants with diarrhea are susceptible to diaper rash. Diarrhea stools can carry certain digestive enzymes that irritate the skin. You can cut down on this irritation by changing your baby’s diapers frequently and cleaning their skin thoroughly with warm water. Using a barrier cream after each diaper change can also be helpful. Avoid baby wipes that contain alcohol. Consult with your pediatrician if the rash continues to worsen or your infant’s skin is bleeding.

Severe diarrhea can also cause adults to develop a rash around their anus. Keep the area as clean and dry as possible. Wash with mild soap and warm water. Call your doctor if the skin in this area blisters or oozes. The rash should clear up after the diarrhea subsides.

If you have a gastrointestinal illness accompanied by a serious rash, it’s not necessarily a case of norovirus. See your doctor for diagnosis.

Learn more about hives »

Reoccurring norovirus

With some illnesses, having a single infection gives you immunity for life. Vaccines can provide immunity to others. But that’s not the case with norovirus. There’s no vaccine, and having it once won’t save you from getting it again. In fact, you can get it many times throughout your life.

If you’re just getting over a bout of norovirus, it’s unclear how long you’ll have temporary immunity. However, there are a variety of strains, so there’s no guarantee you won’t have another bout in short order.

If the virus is going around your family or workplace, take preventive measures to lower the chances of getting reinfected. For example:

  • Wash your hands thoroughly and often, especially after using the toilet, changing a diaper, or tending a sick person. Wash your hands before food preparation or eating. If there’s no soap and water available, use an alcohol-based hand sanitizer.
  • Try not to touch your face with your hands.
  • Don’t share eating utensils, cups, or plates.
  • Wash fruits and vegetables before eating them.
  • Avoid raw seafood.
  • When possible, stay away from infected people. Stay home when you’re sick.

If you often experience vomiting or diarrhea, see your doctor to make sure it’s a norovirus. They may collect a stool sample to confirm the diagnosis.

Norovirus recovery time

Symptoms usually begin about 12 to 48 hours after you’ve come into contact with the virus. In otherwise healthy adults, norovirus isn’t usually a serious problem. Symptoms can be expected to last for one to three days. Most people make a full recovery.

Symptoms can hit infants particularly hard. There may be more vomiting and diarrhea. That can lead to dehydration. Whenever possible, rehydration therapy with oral rehydration solutions, like Pedialyte, is preferred and encouraged. Depending on the severity of symptoms, intravenous fluids and other supportive measures may be needed. Recovery time may be longer.

It might also take more time to recover if you have a weakened immune system or another health problem that makes it harder to fight the virus. Worldwide, norovirus claims the lives of 50,000 children a year. Almost all these deaths occur in developing countries.

Older adults have a weaker immune system, often along with other chronic illnesses. In these cases, dehydration may be more likely. Hospitalization is sometimes necessary, and it may take weeks for the body to rid itself of the virus.

It’s estimated that each year in the United States, 56,000 to 71,000 hospitalizations and 570 to 800 deaths can be attributed to norovirus.