Norovirus

What are noroviruses?

What causes infection with noroviruses?

What are the symptoms of illness caused by noroviruses?

When do symptoms appear?

How long are people contagious?

How long do the symptoms last?

How can norovirus infections be prevented?

What is the treatment for norovirus infection?

How serious is norovirus disease?

What are noroviruses?

  • Noroviruses are a group of viruses that cause "stomach flu" or gastroenteritis in people.
  • Previously, they were called Norwalk-like viruses and were also referred to as calicivirus or as small round enteric (or structured) virus.
  • Noroviruses are commonly found throughout North America and are very infectious.
  • Noroviruses can survive on practically any surface including door handles, sinks, railings and glassware. The virus is able to survive relatively high levels of chlorine.
  • Noroviruses are easily transmitted in environments where people are in close contact, including schools, day-care centres, long-term care facilities, healthcare facilities and cruise ships.
  • They occur throughout the year but are more common in winter.

What causes infection with noroviruses?

  • Noroviruses are found in the stool or vomit of infected people while they are ill and for several days after recovery.
  • Noroviruses are very contagious and can spread easily from person to person. Both stool and vomit are infectious.
  • People can become infected with the virus in several ways, including:

    • Eating food or drinking liquids that are contaminated with norovirus
    • Indirect contact by touching surfaces or objects contaminated with norovirus, and then placing their hand in their mouth
    • Having direct contact with another person who is infected
    • Persons working in day-care centers or nursing homes should pay special attention to children or residents who have norovirus illness.

What are the symptoms of illness caused by noroviruses?

  • Symptoms include nausea, vomiting, diarrhea and stomach cramps.
  • People may have a low-grade fever, chills, headache, muscle aches and fatigue.
  • Illness often begins suddenly, about 24 to 48 hours after exposure.
  • The illness is usually brief, with symptoms lasting only about 1 or 2 days.
  • In general, children experience more vomiting than adults.

When do symptoms appear?

  • Symptoms of norovirus illness usually begin about 24 to 48 hours after ingestion of the virus, but they can appear as early as 12 hours after exposure.

How long are people contagious?

  • People are contagious from the time they begin feeling ill to at least 3 days after recovery. Some people may be contagious for several weeks after recovery.
  • Good hygiene standards, including frequent hand washing, are very important during this period.

How long do the symptoms last?

In most healthy people, acute diarrhea and vomiting usually last eight to twelve hours, and people normally recover within 48 hours. Symptoms may last longer in some people.

How can norovirus infections be prevented?

You can reduce the risk of norovirus infections if you:

  • Wash hands frequently, especially after using the bathroom or changing diapers and before eating or preparing food.
  • Eat food that is well cooked and still hot when served.
  • Wash fruits and vegetables thoroughly before eating.
  • Thoroughly clean contaminated surfaces immediately after an episode of illness with hot, soapy water and then disinfect the area using a household disinfectant.
  • Immediately remove and wash clothing or linen that may be contaminated with stool or vomit.
  • Flush or discard any vomit and/or stool in the toilet and make sure that the surrounding area is kept clean.
  • Avoid shaking out soiled linen and wear household gloves when handling soiled materials.

What is the treatment for norovirus infection?

There is no preventative treatment (vaccine or antiviral medication) for noroviruses and they cannot be treated with antibiotics because antibiotics fight bacteria, not viruses. However, healthy people normally recover on their own within about 48 hours.

Those suffering from illness should drink plenty of fluids to prevent dehydration - a possible serious health effect of norovirus infection. People should drink juice or water to reduce their chance of becoming dehydrated. Sports drinks are not recommended because they do not replace the nutrients and minerals lost during illness. If serious dehydration occurs, the ill person may require re-hydration in hospital.

How serious is norovirus disease?

  • Generally, noroviruses cause unpleasant but self-limiting, gastrointestinal symptoms, such as diarrhea and vomiting.
  • Most people get better within 1 or 2 days, and they have no long-term health effects related to their illness.
  • Sometimes people are unable to drink enough liquids to replace the liquids they lost because of vomiting and diarrhea. These persons can become dehydrated and may need special medical attention.

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