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Department of Health News 

This news item expired on 3/31/2009, so the information below could be outdated or incorrect.

What Are Noroviruses?

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Noroviruses are a group of viruses that cause what we sometimes refer to as “stomach flu”. It often begins suddenly, and may cause the infected person to feel very sick. Symptoms usually last only about 1 or 2 days and children generally vomit more than adults.

NorovirusWhat are the symptoms?
Symptoms usually include:

  • nausea
  • vomiting
  • diarrhea
  • stomach cramps

Sometimes people also have a low-grade fever, chills, headache, muscle aches, and a general sense of tiredness.

How serious is norovirus?
Norovirus is usually not serious. Those with the illness may feel very sick and vomit many times a day, but feel better within 1 or 2 days. Sometimes, however people are not able to drink enough fluids to replace the fluids they lost from vomiting and diarrhea. These people can become dehydrated and may need special medical attention. Dehydration is usually only seen among the very young, the elderly, and those with weakened immune systems.

How are noroviruses passed?
Noroviruses are found in the stool or vomit of someone who has the virus. People can become infected with the virus in several ways, including:

  • eating or drinking things that are contaminated with norovirus
  • touching surfaces or objects contaminated with norovirus, and then placing their hand in their mouth
  • having direct contact with someone who is infected and showing symptoms (for example, when caring for someone who has the virus, or sharing foods or eating utensils with them

When do symptoms appear?
Symptoms of norovirus illness usually begin about 1 – 2 days after contamination with the virus. They can appear as early as 12 hours after exposure.

Are noroviruses contagious?
Noroviruses are very contagious and can spread easily from person to person. Both stool and vomit can transmit the illness. People working in day-care centers or nursing homes should pay special attention to children or residents who have norovirus illness. Special care should be taken with young children in diapers who may have diarrhea.

How long are people contagious?
People infected with norovirus are contagious from the moment they begin feeling ill to at least 3 days after recovery. Some people may be contagious for as long as 2 weeks after recovery.

It is most important for people to use good handwashing practices after recovering from norovirus illness. People who work in the food service industry, healthcare or daycare should remain out of work until at least 3 days after symptoms disappear.

Can norovirus infection be treated?
There is no medicine that works against norovirus and there is no vaccine to prevent infection. Norovirus infections cannot be treated with antibiotics. This is because antibiotics work to fight bacteria and not viruses.

Norovirus illness is usually brief in healthy people. When ill with vomiting and diarrhea, they should drink plenty of fluids to prevent dehydration. Dehydration among young children, the elderly, the sick, can be common, and it is the most serious health effect that can result from norovirus infection. By drinking juice or water, people can reduce their chance of becoming dehydrated. Sports drinks do not replace the nutrients and minerals lost during this illness.

Can norovirus infections be prevented?
Yes. You can decrease your chance of coming in contact with noroviruses by following these preventive steps:

  • wash your hands often, especially after toilet visits and changing diapers and before eating or preparing food
  • wash fruits and vegetables well, and steam oysters before eating them
  • clean and disinfect contaminated surfaces immediately after someone is sick by using a bleach-based household cleaner
  • remove and wash clothing or linens that may be contaminated right away. Use hot water and soap
  • flush any vomit and/or stool in the toilet and make sure that the surrounding area is cleaned well.

More information.