Norovirus

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What is norovirus?

Norovirus is an extremely common cause of diarrhoea and vomiting in humans. It is often called the "stomach flu" although it is not caused by the influenza viruses. The viruses are very small and often difficult to detect. Norovirus is commonly responsible for outbreaks in places where people are in close proximity to each other, such as nursing homes, homes for the aged, hospitals, banquet halls, cruise ships, childcare centres, schools, and restaurants.

Many different viruses can cause gastroenteritis, including noroviruses (Norwalk-like), rotaviruses, adenoviruses, calciviruses, astrovirruses, and picornaviruses. Some viruses tend to cause diarrhoeal disease primarily among people in specific age groups. Rotavirus infection is the most common cause of diarrhoea in infants and young children under 5 years old. Adenoviruses and astroviruses cause diarrhoea mostly in young children, but older children and adults can also be affected. Noroviruses are more prevalent in older children and adults. However, all these viruses could be implicated in an outbreak in a long-term care facility due to the health risks of the population served.

What are the symptoms?

The main symptoms of norovirus infection begin approximately 24-48 hours after exposure to the virus. Symptoms include nausea, vomiting, diarrhoea, and abdominal cramps. A low grade fever may occur and dehydration is possible. The illness usually lasts from one day to three days; however, norovirus can be spread for up to 3 days after the symptoms stop, and some people may carry the virus for up to 2 weeks after the symptoms end.

Although being sick with norovirus can make people feel very unwell for a day or two, almost everybody recovers completely without any long-term problems. However, as with any illness that can cause vomiting or diarrhoea, certain people are at risk for severe dehydration from loss of fluids. These people include infants, young children and persons who are unable to care for themselves, such as the disabled or elderly. Immuno-compromised persons are at risk for dehydration because they may get a more serious illness with greater vomiting or diarrhoea.

Are noroviruses contagious?

Norovirus is very contagious and only a few virus particles are needed to cause illness. People are the only known reservoir for the norovirus and the disease is transmitted easily from person to person. The virus is spread through exposure to food, water, or surfaces contaminated by an infected person. Although it has not been proven, airborne transmission has been suggested as a possible explanation for rapid spread of outbreaks in settings, such as hospitals, nursing homes, daycares, and schools.

How is it treated?

The most important treatment of norovirus is to drink plenty of fluids. This treatment should begin at home. Your physician may give you specific instructions about what kinds of fluid to give. Families with infants and young children may want to keep a supply of oral rehydration solution (ORS) at home at all times and use the solution when diarrhoea first occurs in the child. ORS is available at pharmacies without a prescription. Follow the written directions on the ORS package and use clean or boiled water. Antibiotics have no effect on norovirus.

How is it prevented?

• Thorough hand washing is the best prevention.  Make sure hands are properly washed after using the toilet, changing diapers and before preparing or eating food. Prompt disinfection of contaminated surfaces with household chlorine bleach-based cleaners and prompt washing or disposal of soiled articles or clothing helps to limit the spread of the virus. If food or water is thought to be contaminated by a person sick with norovirus, it should be avoided.
• If you think you have norovirus, the following will help you and help prevent others from getting sick:

  • Drink lots of fluids.

  • Stay home and rest for at least 48 hours after your vomiting and diarrhoea have resolved and you feel well.

  • Do not prepare or handle food that will be eaten by others.

  • See a doctor if your symptoms last longer than three days or you have bloody diarrhoea or a high fever.

  • Wash your hands using soap and water, especially after using the toilet, changing diapers and before eating or preparing food. If water is not available, a waterless hand rinse can be used.

• Since some people can continue to carry the virus for up to 2 weeks after the symptoms end, thorough hand washing and good hygiene should persist after recovery from the illness.

For more information please call Public Health at 519-376-9420 or 1-800-263-3456