Norwalk and Norwalk-like Virus Infection

Norwalk and Norwalk-like viruses cause stomach and intestinal illness which often occurs in outbreaks. Most people are susceptible to the virus since there is no vaccine to prevent it and previous infections do not provide long-term immunity in most cases.

The virus is named after a Norwalk, Ohio elementary school outbreak in 1968. In reality, the virus existed worldwide before then. Only humans get the disease. Outbreak settings include child care facilities, schools, health care facilities, cruise ships, banquets, parties and restaurants.

What are the symptoms associated with this virus?

Most people have nausea and/or vomiting and/or diarrhea. They may also have abdominal cramps, headache, low grade fever, chills and muscle pain. Vomiting occurs more frequently in children, while adults tend to have more diarrhea. Diarrhea due to this virus should not have blood or mucous in it as a rule. If it does, see a physician right away and ask for a stool test to check for a bacterial infection as the cause of the diarrhea.

Infected persons usually recover in 2 hours to several days, (average 24-48 hours), without serious or long-term health effects.

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How do people get Norwalk virus infection?

Contaminated water drunk 4-77 (usually 24-48) hours before illness begins: City of Ottawa water and commercial bottled water are considered safe. Untreated water (or ice made from it) may be the source of the infection.
Contaminated food eaten 4-77 (usually 24-48) hours before illness beings. Raw and undercooked clams and oysters may be contaminated if they have been in contact with raw sewage. Salad ingredients, fruit and other uncooked foods may be contaminated by sick food handlers.
Touching a hard surface contaminated with stool or perhaps vomitus from an infected person and then putting fingers to the mouth before washing one's hands.

When can someone get sick and how long will they be contagious?

The incubation period (time between contracting the virus and having the first symptom) is usually 24-48 hours with a range of 4-77 hours. A person may be contagious to others until 72 hours after the last episode of vomiting or diarrhea.

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How is the virus controlled?

The ill person should not attend a child care facility, school, health care facility or handle food to be eaten by others until 72 hours after the last episode of vomiting or diarrhea.
Those who live in the same household as an ill person may attend a child care facility, school, health care facility or handle food to be eaten by others as long as they immediately go home if they develop nausea, vomiting, diarrhea or abdominal cramps.
Hand washing with soap and water is essential after using the toilet, before preparing food, eating, smoking or other hand to mouth activity. Waterless alcohol hand wash, available at drug stores and some other stores, can also be used if the hands are not visibly dirty. If they are, use soap and water.
Drinking water should be treated, (City of Ottawa water is safe), or from a private well that is tested regularly for contamination.
Cook all shellfish thoroughly.
Wash raw vegetables and fruits thoroughly before eating.
When someone at home is ill, disinfect the bathroom and hard surfaces that may be contaminated with the virus at least daily.

For further information, call Ottawa Public Health at 613-580-6744.

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