Norovirus is a very common and contagious virus that causes vomiting and diarrhea (gastroenteritis). It is sometimes incorrectly called the “stomach flu” but norovirus is not related to the flu/influenza.
Norovirus is the term used to describe a group of viruses that belong to the Calicivirus family. It is often called "winter vomiting disease", viral gastroenteritis, and epidemic viral gastroenteritis or incorrectly “stomach flu". It is a common illness and should not be confused with influenza, which is commonly referred to as the "flu". Influenza viruses usually cause respiratory illness, whereas noroviruses cause gastrointestinal illness. It spreads easily and is one of the most common causes of gastrointestinal outbreaks. Norovirus outbreaks can occur in places where people are close together, like long term care homes, hospitals, and childcare facilities, as well as in the community.
The main symptoms are sudden onset of:
- Nausea and vomiting
- Diarrhea
- Stomach pain and cramps
- Chills
- Fever
Symptoms usually start 12 to 48 hours after infection with the virus, and generally last between 24 to 72 hours. Norovirus can make you vomit and have diarrhea several times a day. This can lead to dehydration (loss of fluids) and weakness. Fluid loss can be a serious problem for the elderly or very young.
The illness is caused by norovirus, but other viruses can cause similar symptoms.
The virus is found in the stool (poop) and vomit of people who are sick. It spreads by the fecal-oral route, which means tiny amounts of fecal material get into someone’s mouth.
- The virus can be spread from person to person through unwashed hands.
- The virus can spread by food, water or ice that has been handled by a person who is sick with norovirus. It is one of the most common causes of foodborne illness.
- Vomiting can create droplets, which can spread the virus by direct inhalation or settling on surfaces.
- The virus can survive on surfaces such as countertops or sink taps for a long time and can be picked up on people's hands. This is an important factor in residential care outbreaks.
- Norovirus is very contagious because it takes very few viruses to start an infection.
Complications are rare. On rare occasions, fluid loss can be a serious problem for the elderly or very young. Norovirus can be a contributing factor to the deaths of some frail, elderly people.
Your healthcare provider might take a sample of your stool or vomit to test for norovirus. A testing method, called the PCR test, is used to identify norovirus.
There is no medication to treat norovirus itself, only for the symptoms. Most people start to feel better on their own within two or three days. Drinking lots of clear fluids while sick is important to prevent dehydration. If diarrhea or vomiting lasts more than two to three days, see a healthcare provider. If three or more people in a facility are sick at the same time, this should be reported to your local public health unit.
There is no vaccine or medicine to prevent norovirus. There are different strains of norovirus and they evolve over time, so you can get sick more than once. After infection, any immunity you have to that strain is short term.
If you have vomiting or diarrhea, do not go to work, school, or childcare. Wait at least 48 hours after your symptoms stop before returning. This is especially important for food handlers and caregivers.
Even after they are well, people can carry the virus in their stool for a few days, so careful hand washing should continue.
Norovirus can spread easily in the home. Cleaning and disinfecting surfaces properly can help prevent others from getting sick.
Cleaning up vomit or diarrhea, or cleaning around the home during and after illness:
- Wear disposable gloves, if available.
- Use paper towels to absorb liquid and pick up any solid material.
- Place used paper towels and waste directly into a plastic garbage bag.
- Clean the affected area with detergent and hot water, then rinse.
- Disinfect the area with bleach solution (four teaspoons bleach in one litre of water).
- Keep the surface wet for at least one minute.
- Throw away used gloves and cleaning materials in the household garbage.
- Wash your hands thoroughly with soap and running water for at least 20 seconds.
Clean and disinfect bathrooms frequently with a dilute bleach solution. Bleach is recommended because many household cleaners are not effective against norovirus.
- Clean up vomit or diarrhea as soon as possible using soap and water.
- Disinfect surfaces after cleaning with a freshly prepared bleach solution:
- Mix four teaspoons (20 mL) of household bleach in one litre of water (1:50 dilution).
- Keep the surface wet with the bleach solution for at least one minute before allowing it to dry.
- If possible, the sick person should stay in a separate room and limit contact with others.
- Household members should wash their hands often with soap and running water.
- Visitors should stay away until everyone is well, and frequently touched surfaces have been disinfected.
- Do not share towels, and machine-wash any towels used by ill household members.
- Wash any soiled bedding as soon as possible.
- Any food that has been handled by an ill person, or food that could have been exposed when someone vomits, should be discarded.
- Dishes or utensils should be washed in a dishwasher, on the hot cycle, or with water and detergent.
