Norovirus facts for kids

Quick facts for kids Norovirus
Synonyms	Winter vomiting bug, stomach bug
This image shows the Norwalk virus under a powerful microscope. The white bar helps you see how tiny it is!
Symptoms	Diarrhea, vomiting, stomach pain, headache
Complications	Dehydration
Usual onset	12 to 24 hours after exposure
Duration	1 to 3 days
Causes	Norovirus
Diagnostic method	Based on symptoms
Prevention	Hand washing, disinfection of contaminated surfaces
Treatment	Supportive care (drinking sufficient fluids or intravenous fluids)
Frequency	688 million cases per year
Deaths	~200,000 per year

Norovirus, sometimes called the winter vomiting bug or stomach bug, is a very common cause of gastroenteritis. This is an illness that affects your stomach and intestines. When you get norovirus, you might have diarrhea, vomiting, and stomach pain. You could also get a fever or a headache.

Symptoms usually start about a day after you've been exposed to the virus. Most people feel better within one to three days. It's not common to have serious problems, but some people, especially very young children, older adults, or those with other health issues, can get dehydration. This means their body loses too much fluid.

The norovirus usually spreads when tiny bits of poop or vomit from an infected person get into food or water, or onto surfaces. You can also catch it by touching an infected person. It can even spread through tiny drops in the air from someone's vomit. Washing your hands well and cleaning surfaces are the best ways to stop it from spreading.

There isn't a special medicine or vaccine for norovirus. The main treatment is to drink plenty of fluids to avoid dehydration. Drinks like oral rehydration solutions are best. Other drinks without caffeine or alcohol can also help.

Norovirus causes about 685 million cases of illness and 200,000 deaths worldwide each year. It's common everywhere. Young children under five are most often affected. In some parts of the world, it causes about 50,000 deaths in this age group. Norovirus infections happen more often in winter. It often causes outbreaks, especially where many people live close together, like on cruise ships or in schools. The virus is named after Norwalk, Ohio, where an outbreak happened in 1968.

How Norovirus Makes You Feel

If you get norovirus, you might feel nausea (like you need to throw up), actually vomit, have watery diarrhea, and abdominal pain. Sometimes, you might also lose your sense of taste. These symptoms usually start about 24 hours after you've been exposed to the virus.

You might also feel tired, weak, have muscle aches, headaches, and a slight fever. The good news is that the illness usually gets better on its own. While having norovirus can be very unpleasant, it's usually not dangerous. Most people recover completely within two to three days.

For people with weaker immune systems, norovirus can sometimes cause a longer-lasting infection. This can lead to more serious problems with their intestines.

How Norovirus Spreads

Noroviruses spread easily from person to person. They can also spread through contaminated water and food. When someone with norovirus vomits or flushes a toilet after having diarrhea, tiny virus particles can become airborne. You can get infected by eating food or breathing air near where someone has been sick, even if it's been cleaned up.

People can still spread the virus for many weeks after their symptoms have gone away. Vomiting is especially good at spreading the infection through the air. For example, in one case, a person who vomited in a restaurant spread the infection to many other diners, even those far away.

Outbreaks can happen quickly. In one international scout jamboree, one sick person infected many others before better hygiene rules were put in place.

Contaminated shellfish and salad ingredients are often linked to norovirus outbreaks. Shellfish that isn't cooked enough (below 75°C) can be risky. Other foods can get contaminated by infected people who prepare them. Many outbreaks have been traced back to just one infected food handler.

In 2017, over 700 people in Quebec, Canada, got sick from norovirus. The cause was frozen raspberries imported from China. Canadian authorities recalled these products.

The US Centers for Disease Control and Prevention (CDC) reported a rise in norovirus cases on cruise ships in 2023. This was the highest number of outbreaks since 2012.

What Norovirus Looks Like

Noroviruses are a group of viruses that belong to the Caliciviridae family. They are very tiny and don't have an outer "envelope" like some other viruses. There are different types of noroviruses, which scientists group together. Most noroviruses that make humans sick belong to two main groups, GI and GII. One type, called GII.4, causes most of the outbreaks around the world.

What Happens When You Get Norovirus

When you get infected with norovirus, the virus makes copies of itself inside your small intestine. This causes the main symptoms of gastroenteritis. You'll feel nausea, strong vomiting, watery diarrhea, and stomach pain. These symptoms usually start 12 to 48 hours after you're exposed and last for one to three days.

Sometimes, you might also lose your sense of taste, feel very tired, weak, have muscle aches, a headache, a cough, or a low-grade fever. The illness usually goes away on its own.

Serious illness is rare. While people often go to the emergency room, they usually don't need to stay in the hospital. In the United States, about 570–800 deaths happen each year from norovirus. Most of these are in very young children, older people, and those with weak immune systems. For these groups, dehydration or an imbalance of important body salts can be dangerous if not treated.

How Doctors Diagnose Norovirus

Doctors can usually tell if you have norovirus based on your symptoms. To be absolutely sure, they can use special tests called polymerase chain reaction (PCR) assays. These tests can find even a tiny amount of the virus in a few hours. They are very good at detecting the virus.

Stopping Norovirus: Prevention Tips

After you've had norovirus, your body builds up some protection (called immunity) against that specific type of virus. This protection can last from six months to two years. However, it doesn't fully protect you from other types of norovirus.

Hand Washing and Cleanliness

Washing your hands with soap and water is the best way to stop norovirus from spreading. You should wash your hands often, especially after using the bathroom and before eating or preparing food.

Alcohol-based hand sanitizers can help, but they are not as effective against norovirus as washing your hands with soap and water. This is because norovirus doesn't have a fatty outer layer that alcohol usually breaks down. Some studies show that alcohol mixed with acid, like from lemon juice, can be more effective.

Surfaces that might have norovirus particles on them should be cleaned with a solution of household bleach and water, or other special disinfectants that work against norovirus.

Keeping Hospitals Safe

In places like hospitals, it's very important to prevent norovirus from spreading to other patients. This involves regular and thorough cleaning. Special cleaning systems are used in areas with medical equipment that could be damaged by strong cleaning chemicals.

The CDC has guidelines for hospitals to prevent norovirus outbreaks. These include things like keeping sick patients separate, making sure staff wash their hands, and cleaning the environment carefully.

Hope for a Vaccine

Scientists are working on a vaccine to protect against norovirus. Trials for a vaccine have been ongoing, with phase 2b trials completed in 2020. This vaccine uses a "virus-like particle" that looks like the outside of the norovirus but doesn't contain any of the virus's genetic material. This means it can't cause an infection but can teach your body to fight off the real virus.

How Long Norovirus Lasts on Surfaces

Norovirus is very tough and can survive for a long time outside the human body. It can stay on hard and soft surfaces for weeks. It can even survive for months or years in contaminated still water. One study found the virus still on food preparation surfaces seven days after they were contaminated.

Finding Norovirus in Food

Government labs, like the Food and Drug Administration (FDA) in the US, use special tests to find norovirus in foods like clams and oysters.

What to Do if You Get Norovirus

There is no specific medicine that cures norovirus illness. The main goal of treatment is to prevent problems like dehydration. This means drinking plenty of fluids to replace what your body loses from vomiting and diarrhea. Oral rehydration solutions are often recommended. Sometimes, doctors might give medicines to help with vomiting or diarrhea.

Norovirus Around the World

Norovirus causes about 18% of all cases of sudden stomach and intestinal illness worldwide. It's very common in both wealthy and developing countries. It causes more illness in people who are at home or visiting a doctor's office than in those already in the hospital.

Norovirus is extremely contagious. It's estimated that one sick person can easily infect many others. You only need to come into contact with a tiny amount of the virus (as few as 10 virus particles) to get sick.

In the United States, there are about 21 million cases of norovirus each year. This means about 6,270 cases for every 100,000 people.

Norovirus is a common cause of outbreaks on cruise ships. The CDC tracks these outbreaks. For example, there were 12 outbreaks in 2015 and 10 in the first part of 2016. An outbreak can affect more than 25% of passengers.

The Story Behind the Name

The norovirus was first called the "Norwalk agent." This was after an outbreak of stomach illness among children in Norwalk, Ohio, in November 1968. In 1972, scientists used powerful microscopes to find the virus in stored samples and named it "Norwalk virus."

Later, scientists learned more about these viruses. In 2002, the official name "norovirus" was approved for the group of viruses. However, in 2011, a group of scientists suggested that the media and health organizations should still use "Norwalk virus" when talking about outbreaks. This was partly because of concerns that the name "Norovirus" might sound too similar to a common family name in Japan.

Besides "Norwalk agent" and "Norwalk virus," this illness has also been called "winter vomiting disease" or "winter vomiting bug."

See also

In Spanish: Norovirus para niños