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Norovirus

 

Definition

Norovirus (formerly Norwalk-like virus) is often referred to as "winter vomiting disease, viral gastroenteritis, epidemic viral gastroenteritis" or incorrectly as "stomach flu". It is a common illness and should not be confused with influenza, which is commonly referred to as the "flu". Influenza virus causes an illness with symptoms like cough and sore throat, fever, muscle aches, headaches and tiredness, whereas gastroenteritis basically involves the digestive system.  

Symptoms

The main symptoms are sudden onset of

  • nausea
  • cramping
  • chills
  • fever
  • usually vomiting and/or diarrhea are also present.

Symptoms usually start 24 to 48 hours after infection with the virus, and generally last between 24 to 36 hours. Fluid loss can be a serious problem for the elderly or very young. 

 

Causes

The illness is caused by norovirus, although similar viral gastroenteritis illnesses may be caused by other viruses in the "small, round-structured virus" group.

  • The main source of the virus is stool and vomit from infected people, and is passed along through what is called the fecal-oral route. 
  • The virus can be spread from person to person on unwashed hands. 
  • The virus can also be spread by food, water or ice that has been handled by a sick person.

It is considered to be one of the most common causes of foodborne illness. 

  • Vomiting may spread the virus, in aerosol droplets
  • 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, an important factor in residential care outbreaks. 
  • It takes very few viruses to start an infection.
 

Complications

Complications are rare. Most of the time people have symptoms which last 24-36 hours. 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.   

Tests and Diagnosis

Norovirus is diagnosed through a specimen of vomitus or diarrhea (stool). A testing method, called the PCR test, is used to identify norovirus. Before the PCR test became available, electron microscopy was used to identify norovirus, but the success rate of finding the virus was low.  

Treatment and Drugs

Drinking lots of clear fluids while ill is important. If diarrhea or vomiting lasts more than two to three days see a doctor. If three or more persons are ill at the same time, this should be reported to your local public health unit. There are no drugs for the treatment of norovirus itself, only for the symptoms.  

Prevention

 

There is no vaccine or medicine that can prevent norovirus. There are different strains of norovirus, so people who have had it once can get norovirus again, and there is only temporary immunity to the strain that has just infected a person.

  • The key to reducing person-to-person spread of norovirus is hand washing. A proper hand wash requires warm running water, soap and rubbing hands together for about 30 seconds. Cleaning fingertips is important, and a nail brush is helpful for cleaning under the nails.
  • Anyone who is ill should avoid going to work, especially food handlers or caregivers, until at least 48 hours after symptoms have stopped. Even after they are well, people can carry the virus in their stool for a few days so careful hand washing should continue.
  • If several members of a family are sick with vomiting and diarrhea, clean up at once and disinfect the floors, counters and furniture with a dilute bleach solution (at least one part household bleach to 50 parts water - e.g. four teaspoons of bleach [20mls] to one litre of water - exercise caution with surfaces that can be damaged by bleach) once everyone is well. Visitors should be asked to stay away while there are sick people in the house and for a few days after until the house is cleaned.
  • If only one person is sick, other family members may become sick after 24-48 hours. The sick person should try to keep to his or her own room and have little contact with the other family members. Everyone must do careful handwashing.
  • Cleaning up after a vomiting accident, using hot water and detergent is important. Surfaces should then be wiped down with a dilute bleach solution to kill the virus. Any food that has been handled by an ill person, or food that could have been exposed when someone vomits, should be discarded. 
  • It is recommended that the person cleaning up vomit or diarrhea wear a surgical mask, easily obtained at any pharmacy; disposable, waterproof gloves and clothes that can be changed and washed in hot water.
  • Dishes or utensils should be washed in a dishwasher, on the hot cycle, or with hot water and detergent.
  • Laundry should also be washed in hot water and detergent.
  • Bathrooms and toilet areas need special care. They should be disinfected often with a dilute bleach solution. Household cleaners other than bleach are not effective.
  • When cleaning up vomit or feces, or just cleaning around the house during and after illness:

1) Wear disposable gloves if possible.

2) Use paper towels to soak up excess liquid. Transfer these and any solid matter directly into a plastic garbage bag.

3) Clean the soiled area with detergent and hot water, and rinse. Do not use the cleaning cloth or sponge to clean other areas of the house as this may lead to further spread of the virus.

4) Wipe area with freshly made bleach solution (as above). Keep the area wet with sanitizer for 2 minutes.

5) Dispose of all cleaning cloths and gloves into a garbage bag.

6) Wash hands thoroughly using soap and running water for at least 30 seconds.

  • Pay attention to bathrooms and any commonly touched areas.
  • Do not share towels, and quickly machine-wash any towels used by ill family members.
  • Wash any soiled bedding as soon as possible on a "hot cycle".
  • Soiled carpets should be cleaned with detergent and hot water, if possible.   
Last Updated: February 4, 2011