Infectious Diseases

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Norovirus (Norwalk-like) Virus Infection

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What is Norovirus infection?

Norovirus was recently approved as the official name for the group of viruses provisionally described as “Norwalk-like viruses”. Norovirus is a common cause of viral gastroenteritis. This illness often occurs during the winter months and is often referred to as ‘stomach flu’ or ‘Winter Vomiting Disease’. Norovirus infections have been linked to outbreaks of vomiting and/or diarrhea in institutions such as child-care centres, long-term care facilities, camps and schools. Norovirus outbreaks have also been identified in cruise ships and within households.

How is Norovirus transmitted?

Norwalk virus infection is spread from person-toperson. You can acquire the virus by coming into contact with an ill person’s vomit or diarrhea. Common hard surfaces such as a doorknob, phone, or handrail have been implicated in the transmission of the disease because they can be easily contaminated by an ill person’s unwashed hands. If proper handwashing techniques are not used, direct contact with an ill person’s contaminated hands, or cleaning up vomit or diarrhea of an ill person can spread the infection from person to person. It can also be transmitted by ingesting food or water that is contaminated with the virus.

What are the symptoms of Norwalk-like virus infection?

Most individuals with Norovirus will experience one to three days of nausea, vomiting, cramps and watery diarrhea. Symptoms can also include headache, fatigue, chills and muscle pain. Severe illness or hospitalization caused by Norovirus infection is uncommon. Infected individuals usually recover in two to three days without serious or longterm health effects. Seek medical advice if diarrhea is bloody and/or accompanied with a high fever, the symptoms last longer than 72 hours, or you are becoming dehydrated.

How soon do symptoms appear?

Symptoms usually appear one to two days after exposure to the virus.

How is Norwalk-like virus infection diagnosed?

Your physician may order a stool specimen to diagnose Norovirus infection. Testing is usually not necessary for healthy adults if symptoms resolve in two to three days.

What is the treatment for Norovirus?

There is no specific treatment for Norovirus infection. You should get bed rest and drink plenty of fluids. People who become severely dehydrated should seek medical attention.

What can be done to prevent Norwalk-like virus?

  • Wash your hands thoroughly for at least 10 seconds with soap and warm water after using the toilet and before preparing any food, before you eat and after touching contaminated surfaces.
  • Drink only potable water (treated water) - surface waters (lakes, streams, springs etc.) cannot be considered potable unless treated
  • Do not prepare food for others if you have symptoms of a Norwalk virus infection such as vomiting and/or diarrhea. Get plenty of rest and stay home until you are no longer infectious to others, which is a minimum of 48 hours.
  • Disinfect surfaces (e.g. doorknobs, railings, and toilets) frequently using household disinfectant or a solution of one part bleach to 10 parts water.
  • Wear gloves when cleaning up vomit or diarrhea

Are there any special concerns about Norwalk-like virus infection?

The symptoms of Norwalk virus infection may be more severe for older individuals, young children and those with underlying medical conditions who may become dehydrated due to vomiting and diarrhea.

References

American Public Health Association. (2004). Norwalk-like disease. Epidemic Viral Gastroenteropathy. In D. Heymann (Ed.), Control of communicable diseases manual (18th ed., p. 227-9). Washington, DC: American Public Health Association. Toronto Public Health. (2002, December 12). “Norwalk Virus Infection”.

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