Fact Sheet headerWhat are norovirus infections?

Noroviruses are a group of viruses that cause an infection in the stomach and intestines called gastroenteritis.  Symptoms of norovirus can include nausea, vomiting and/or diarrhea. Some people call it the “stomach flu” but it is not caused by the influenza virus.

Norovirus is very contagious and has been linked to outbreaks of vomiting and/or diarrhea in day nurseries, schools, long-term care homes, cruise ships, camps, dormitories, restaurants, households and other places where people gather in groups.

How do you get norovirus infection?

Noroviruses are found in the stool and in the vomit of ill persons.

The virus spreads very easily by:

  • Having close contact with another person who is infected and has symptoms
    • People infected with norovirus are most contagious from the moment they begin feeling ill to at least three days after recovery. In some cases people may be contagious for as long as two to three weeks after their symptoms have stopped.
  • Eating food or beverages that are contaminated with the virus
    • Food may become contaminated by food handlers who are ill with norovirus, especially if they do not wash their hands properly after using the washroom and before touching food.  Food such as shell fish can also be contaminated at the source.
  • Transfer from contaminated surfaces or objects
    • Norovirus can survive on surfaces for up to 12 days. As an example, children may become ill if they touch contaminated toys and then put their fingers in their mouths.

Only a few virus particles on your food or hands can make you sick.

Who is at risk of getting norovirus infection?

Anyone can get norovirus infection since it is highly contagious.  Most people will recover with no complications. The symptoms of norovirus infection may be more severe for infants, young children, the elderly and those with weakened immune systems.

What are the symptoms of norovirus infection?

Symptoms often begin suddenly, about 24 to 48 hours after ingesting the virus, but can start as soon as 12 hours after exposure.  Most individuals with norovirus infection will experience one to three days of:

  • Nausea
  • Vomiting
  • Watery diarrhea

Other symptoms may include fever, headache, and stomach cramps. Severe illness or hospitalization is not common. Infected individuals usually recover within two to three days without serious or long-term health effects. Dehydration is the most common complication, especially among young children and the elderly.

If diarrhea is bloody, accompanied with a high fever or if the symptoms last longer than 72 hours contact your doctor. Your illness may be due to something other than norovirus.

Is norovirus infection the same as the “flu”?

People often refer to the symptoms of norovirus infection as the “stomach flu”. However, influenza (the flu) is a respiratory illness with symptoms of cough, sore throat and fever. While receiving the annual influenza vaccine is important each winter and is free for anyone who works, attends school or lives in Ontario, the influenza vaccine will not protect you against a norovirus infection.

How can norovirus infection be prevented? 

  • Keep your hands clean
    • Wash hands often with soap and warm water after using the toilet, changing diapers and before preparing, handling or eating food. If soap and water is not available and hands are not visibly soiled, use an alcohol-based hand sanitizer with a minimum of 70% alcohol. Thoroughly washing hands with soap and water is preferred to prevent the spread of norovirus.
  • Do not prepare food for others if you have symptoms of vomiting or diarrhea
  • Thoroughly and frequently disinfect environmental surfaces and equipment
    • Use a chlorine bleach disinfectant, at a concentration of 1000 parts per million (ppm) to 5000 parts per million (ppm) (based on household bleach containing 5.25% sodium hypochlorite), especially in areas that are touched often (such as telephones, door handles, gym equipment, bed side rails).
    • The bleach solution must be made fresh daily to be most effective. Ensure the area stays wet with the solution for a minimum contact time of 10 minutes to kill norovirus.

1:50 (1000 parts per million) bleach solution:

2 teaspoon (10 millilitres) bleach plus 2 cups (495 milliltres) water or

¼ cup (60 millilitres) bleach plus 12 cups (3000 millilitres) water

1:10 (5000 parts per million) bleach solution:

¼ cup (60 millilitres) bleach plus 2 ⅓ cups (550 millilitres) water or

1 cup (250 millilitres) bleach plus 9 cups (2250 millilitres) water

  • Stay home from school, day care or work if you are ill with diarrhea or vomiting
    • Do not return until being symptom-free for at least 48 hours (two days). This is especially important for those who work with food, the elderly or at a hospital.

Is there a vaccine for norovirus?

No. There currently is no vaccine available in Canada to prevent norovirus infections.

How is norovirus infection diagnosed?

Doctors generally diagnose norovirus based on symptoms that resolve after two to three days. However, a stool sample may be suggested in certain circumstances.

Can norovirus infection be treated?

There is no specific treatment for norovirus infection. Antibiotics are not useful because the illness is caused by viruses, not bacteria. Ill persons should drink plenty of fluids since dehydration is a common complication from norovirus infection.

February 27th, 2019