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Noroviruses

Norwalk and Norwalk-like viruses

Dec 13, 2006

Norovirus (electron microscopy), Centers for Disease Control

Noroviruses are a group of single-stranded RNA, non-enveloped viruses that cause gastroenteritis in human.

Noroviruses belong to the family of caliciviruses (genus Norovirus, family Caliciviridae). Prior to 2002 when the term noroviruses was officially adopted, noroviruses were called Norwalk viruses, Norwalk-like viruses, or small round structured viruses.

Humans are the natural host of noroviruses. Noroviruses are common throughout North America and are very infectious: as few as 100 viral particles are required to cause infection. Noroviruses are relatively stable in the environment, and can survive freezing and heating to 60°C (140°C). Noroviruses are readily passed directly through person-to-person, and indirectly through ingestion of contaminated food or water, and contact with contaminated surfaces: noroviruses survives extremely well on surfaces such as door handles, sinks, glassware, utensils, telephones, computer keyboards, carpets, sheets, clothing, diapers and many other items that we come into contact with daily.

Noroviruses cause gastroenteritis (stomach flu). Illness begins suddenly (24 to 48 hours after ingestion), and people who become infected generally feel very ill, vomiting many times a day. Most people infected with Norovirus will have both vomiting and diarrhea. Illness is usually self-limiting with symptoms usually lasting 1 to 2 days, although complications such as acute dehydration may be seen in the very young, the very old and immunocompromised individuals. Adequate fluid replacement is necessary to prevent dehydration resulting from fluid loss through vomiting and diarrhea. Fluid replacement is especially important in those most at risk of complications.

Symptoms most often associated with Norovirus infection:

nausea,
vomiting,
diarrhea.

Additional symptoms sometimes associated with Norovirus infection:

abdominal pain,
low-grade fever,
chills,
headache,
muscle aches,
fatigue.

Norovirus infection affects all age groups and is easily transmitted among people in close-shared environments such as day-cares, schools, military facilities, healthcare and long-term care facilities, and cruise ships. Infection is more common in winter, possibly related to closer contact of persons during the winter months.

Viral particles are passed in the stool and vomit of infected persons for up to 4 days following recovery – some people remain contagious for 2 weeks. Hand-hygiene for those infected, and for care-givers and contacts is extremely important to prevent the spread of norovirus infection.

Noroviruses cannot be treated with antibiotics as they are effective against bacteria but not viruses. Research is ongoing to develop a vaccine to prevent the spread of norovirus infections.

Sources:

Public Health Agency of Canada

Centers for Disease Control and Prevention

The copyright of the article Noroviruses in Microbiology is owned by Judy Arbique. Permission to republish Noroviruses in print or online must be granted by the author in writing.

Comments

Dec 18, 2006 11:53 AM

Rosemary Drisdelle :

When norovirus struck my son's university recently, measures taken in the residence really impressed me - specific toilets and sinks in the shared washrooms were designated "for those with symptoms of norovirus." As long as there is more than one washroom available, families could do this at home to greatly reduce the risk of transmission between family members. Great idea!

Dec 19, 2006 8:10 AM

Judy Arbique :

Thanks for your input. That does sound like a great idea. It is very difficult to keep Norovirus from spreading in a small environment such as a university, let alone a home...especially if a child is infected! Your efforts to support and comfort your child will likely result in you contracting the virus. A friend of mine recently encountered this when her 2 hear old daughter was ill with Norovirus...being a lab tech, she was well aware of the need for cleansing of anything and everything that the child came in contact with, but still ended up getting ill herself. Dedicating a household washroom for 'symptomatic' only might prove very helpful in controlling transmission to other family members...not likely to have helped in my friend's case with a young child, but has great potential for older more self-sufficient contacts!

2 Comments