Norovirus
Introduction
The norovirus group of viruses are the most common cause of gastroenteritis (upset stomach) in the UK. They are also known as "small round structured viruses" (SRSV) or "Norwalk-like viruses".
Norovirus infections are sometimes called "winter vomiting disease", because people often get them during the winter months. However, they can occur at any time of the year.
Symptoms of a norovirus infection include nausea, vomiting, diarrhoea and in some cases a fever, headache, stomach cramps and aching limbs. Symptoms can last for 12 to 60 hours, but most people recover within two days (see Symptoms for more information).
How noroviruses are spread
It is estimated that noroviruses infect between 600,000 and one million people in the UK every year. Norovirus infections occur in people of all ages and outbreaks of the illness are common, particularly within contained environments such as hospitals, nursing homes and schools. This is because the norovirus spreads very easily from person to person and can survive for several days in a contaminated area.
Noroviruses can be spread through contact with an infected person, through contact with surfaces or objects that are contaminated with the virus, or by consuming contaminated food or water.
After having a norovirus infection it is possible to become infected again, because immunity to the virus only lasts for a short period of time.
Outlook
There is no specific treatment for a norovirus infection and usually you will not need to see a doctor as the symptoms leave after a couple of days. See Treatment for information on how to care for yourself or your child at home.
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Symptoms
The symptoms of a norovirus infection usually start one to two days after becoming infected, but they can start after 12 hours.
The first symptom is usually a sudden onset of nausea, which is followed by projectile vomiting and watery diarrhoea. Some people may also have:
- a raised temperature (over 38C/100.4F)
- headaches
- stomach cramps
- aching limbs
Symptoms normally last from 12 to 60 hours but most people make a full recovery within two to three days. There are no long-lasting effects from having a norovirus infection.
Dehydration
The severe vomiting and diarrhoea caused by the norovirus can lead to dehydration (a lack of fluid in the body).
Dehydration is more of a risk in the very young and the elderly. Symptoms of mild dehydration include:
- dizziness or light-headedness
- headache
- tiredness
- dry mouth, lips and eyes
- dark, concentrated urine
- passing only small amounts of urine (fewer than three or four times a day)
When you are severely dehydrated, you may experience more extreme symptoms such as dry, wrinkled skin, an inability to urinate, a weak pulse and low level of consciousness.
Mild dehydration is common and can be easily reversed by drinking lots of fluids. However, severe dehydration can lead to serious complications and be fatal in some cases. For more information, see the topic dehydration.
If you or your child have any of the symptoms of severe dehydration after catching a norovirus infection, seek medical attention as soon as possible.
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Diagnosis
Norovirus infections can be diagnosed by sending a sample of your stools to be tested in a laboratory. However, this is not usually necessary because treatment is the same for all causes of gastroenteritis.
Noroviruses are the most common cause of gastroenteritis, so if you have a sudden episode of vomiting and diarrhoea, it is likely you have been infected with a norovirus
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Treatment
There is no specific treatment for a norovirus infection and you will usually not need to visit a doctor. Instead:
- Stay at home.
- Take paracetamol to relieve symptoms of any fever.
- Drink plenty of water to replace the fluids lost through diarrhoea and vomiting. This prevents dehydration.
Drinking plenty of fluids is particularly important for young children and the elderly, who are more prone to dehydration.
Try to eat a light diet of foods that are easy to digest, such as soup, rice, pasta and bread. Babies should be given their normal feed throughout.
To reduce the risk of passing the virus onto others, wash your hands regularly and stay at home until you are clear of symptoms for 48 hours.
If your symptoms continue for more than three days or you feel severely dehydrated, seek medical attention immediately.
Dehydration
If you are finding it hard to keep down fluids, try to take small sips more frequently to keep yourself hydrated.
Rehydration solution
If you are dehydrated, you will have lost sugars and salts from your body as well as fluids. Rehydration solution can help replace all the minerals you have lost and re-establish a balance of fluids in your body. Solutions usually come in a powder form that you mix with water and drink. These are available from pharmacies, so ask your pharmacist or GP for advice.
Severe dehydration
If you are severely dehydrated, you may need to go into hospital. Fluids can be given directly into your body by a naso-gastric tube (up the nose) or a saline drip (into a vein).
For more information, see treating dehydration.
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Prevention
It is not always possible to avoid getting a norovirus infection, but good hygiene can help to limit the spread of infection.
You can take the following steps to help stop the virus spreading:
- Wash your hands frequently and thoroughly, particularly after using the toilet and before preparing food.
- Do not share towels and flannels.
- Disinfect any surfaces or objects that could be contaminated with the virus. It is best to use a bleach-based household cleaner. Always follow the instructions on the cleaning product.
- Wash any clothing or bedding that could have become contaminated with the virus. Wash the items seperately and on a hot wash to ensure that the virus is killed.
- Flush away any infected faeces or vomit in the toilet and keep the surrounding toilet area clean.
- Avoid eating raw, unwashed produce and only eat oysters from a reliable source. Oysters have been known to carry the norovirus.
If you have a norovirus infection, avoid direct contact with others, and preparing food for others, until at least 48 hours after your symptoms have gone. You may still be contagious, even though you no longer have sickness or diarrhoea.
Avoid visiting hospitals if you have had the typical symptoms of norovirus infection in the past 48 hours. Norovirus infection is more serious and even more easily spread among people who are already ill. You may be asked to rearrange outpatient appointments if you have had recent symptoms.
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