Norovirus, sometimes known as the winter vomiting bug, is the most common stomach bug in the UK.
The virus is highly contagious. It can affect people of all ages and causes vomiting and diarrhoea.
There's no specific cure for norovirus, so you have to let it run its course. It's usually mild and shouldn't last more than a couple of days.
The period from when you're infected to when you start to show symptoms (the incubation period) usually lasts between 12 and 48 hours. You may be infectious to other people during this time.
Although having norovirus can be unpleasant, it's not usually dangerous and most people make a full recovery within a couple of days without having to see their GP.
There are at least 25 different strains of noroviruses known to affect humans. They're the most common cause of stomach bugs (gastroenteritis) in the UK.
Each year, it's estimated that between 600,000 and 1 million people in the UK catch norovirus. The illness is sometimes called the "winter vomiting bug" because it's more common in winter. However, you can catch the virus at any time of the year.
What should I do?
If you have norovirus, follow the steps below to help ease your symptoms:
drink plenty of water to avoid dehydration
take paracetamol for any fever or aches and pains
if you feel like eating, eat foods that are easy to digest
stay at home – don't go to see your GP because norovirus is contagious and there's nothing your GP can do while you have it
contact your GP to seek advice if your symptoms last longer than a few days or if you already have a serious illness
Extra care should be taken to prevent babies and small children who have diarrhoea and vomiting from dehydrating by giving them plenty of fluids. Babies and young children can still drink milk.
Don't worry if you're pregnant and you get norovirus. There's no risk to your unborn child.
Preventing norovirus spreading
Norovirus is easily spread. If an infected person doesn't wash their hands before handling food, they can pass the virus on to others. You can also catch it by touching contaminated surfaces or objects.
Follow the measures below to help prevent the virus spreading.
wash your hands frequently
don't share towels and flannels
disinfect surfaces that an infected person has touched
Outbreaks of norovirus in public places, such as hospitals, nursing homes and schools, are common because the virus can survive for several days on surfaces or objects touched by an infected person.
If you have norovirus, you may continue to be infectious for a short period after your symptoms stop. You should therefore avoid preparing food and direct contact with others for at least 48 hours after your symptoms disappear.
Further help and advice
Don't go to see your GP – norovirus is highly contagious and there's nothing your GP can do while you have it.
Symptoms of norovirus
The first sign of norovirus is usually suddenly feeling sick followed by forceful vomiting and watery diarrhoea.
Some people may also have:
a raised temperature (over 38°C/100.4°F)
painful stomach cramps
Symptoms usually appear one to two days after you become infected, but they can start sooner. Most people make a full recovery within a couple of days.
Apart from the risk of dehydration, norovirus isn't usually dangerous and there are no long-lasting effects from having the illness. However, it can be pretty unpleasant while you have it.
The main risk from norovirus is dehydration from your body losing water and salts from vomiting and diarrhoea.
Thirst is the first sign of dehydration. Other symptoms include:
dizziness or lightheadedness
dry mouth, lips and eyes
dark, concentrated urine
only passing small amounts of urine (less than three to four times a day)
Mild dehydration is common and can easily be reversed by making sure you have plenty to drink.
The young and elderly are more at risk of becoming dehydrated. It's therefore very important that you seek medical attention immediately if you think your child or an elderly relative is becoming dehydrated.
If you don't replace the lost fluid, dehydration will get worse and could lead to complications, such as low blood pressure and kidney failure. It can even be fatal.
As well as severe thirst, you may also have:
dry, wrinkled skin
an inability to urinate
a weak pulse
a rapid heartbeat
cold hands and feet
If you or your child has any symptoms of severe dehydration after catching a norovirus infection, seek medical attention as soon as possible.
The only way of diagnosing norovirus is to test a stool sample in a laboratory.
However, this isn't usually necessary because treatment is the same for all causes of stomach bugs.
If you have a sudden episode of vomiting and diarrhoea, it's likely you have norovirus.
Can I get norovirus again?
Yes, you can get norovirus more than once. The virus is always changing, which means your body is unable to build up resistance to it.
There's no specific treatment for norovirus.
You don't need to see your GP because your body should fight off the infection within a couple of days.
It's very important that you drink plenty of fluid. If necessary, you can take paracetamol to treat fever, aches and pains.
Eat foods that are easy to digest, such as soup, rice, pasta and bread. Babies should continue with their normal feeds.
To reduce the risk of passing the virus on to others, wash your hands regularly and stay at home until you've been clear of symptoms for 48 hours.
Drinking plenty of fluids is particularly important for young children and the elderly because they're more vulnerable to dehydration. They'll need urgent medical treatment if they start to show signs of dehydration, such as a headache, dizziness or lightheadedness.
If you have norovirus, you'll need to drink more than your usual daily amount to replace the fluids lost from vomiting and diarrhoea.
Suitable drinks include water, squash and fruit juice. If you're finding it difficult to keep fluids down, try taking small frequent sips to keep yourself hydrated.
Infants and small children should take frequent sips of water, even if they vomit. A small amount of fluid is better than none. Avoid giving fruit juice and carbonated drinks to children under five years of age because these can make diarrhoea worse.
If you're worried that you're becoming dehydrated, your GP or pharmacist may advise you to take rehydration drinks.
You can buy sachets of rehydration powders from your pharmacy which you add to water (follow the instructions on the packet). Rehydration drinks provide the correct balance of water, salt and sugar for your body.
Not all rehydration drinks are suitable for children. Check which ones are suitable with your GP or pharmacist.
You should also seek immediate medical help if your symptoms continue for more than three days or if you feel severely dehydrated at any time.
Advice for parents
If your child has norovirus, keep them away from school or nursery for at least 48 hours after their last episode of diarrhoea or vomiting.
Children should not swim in a swimming pool for two weeks after the last episode of diarrhoea.
Norovirus is the most common cause of stomach bugs in the UK
Looking after a sick child
It's important to listen to your child if they're ill. For example, they may be more comfortable on the sofa with a blanket or duvet than in bed.
Make sure that:
the room is airy but not draughty – if it's too warm, they'll probably feel worse
you give them plenty to drink – they may not want anything to eat for the first day or so
they get plenty of rest – encourage them to doze off when they need to
It's not always possible to avoid getting norovirus, but good hygiene measures can help limit the spread of the virus.
The advice below will help stop the virus spreading.
Wash your hands frequently and thoroughly with soap and water, particularly after using the toilet and before preparing food.
Don't share towels and flannels.
Disinfect any surfaces or objects that could be contaminated with the virus. It's best to use a bleach-based household cleaner.
Wash any items of clothing or bedding that could have become contaminated with the virus. Wash the items separately and on a hot wash to ensure that the virus is killed.
Flush away any infected faeces or vomit in the toilet and clean the surrounding toilet area.
Avoid eating raw, unwashed produce and only eat oysters from a reliable source. Oysters have been known to carry the norovirus.
If you have norovirus, avoid direct contact with other people and preparing food for others until at least 48 hours after your symptoms have disappeared. 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 in the past 48 hours. Some hospitals may request you avoid visiting if you've had symptoms within the past 72 hours. Norovirus is more serious and even more easily spread among people who are already ill.
You may be asked to rearrange a medical appointment if you have had norovirus symptoms recently.
Raw or lightly cooked shellfish has been known to infect a person with norovirus.
A study published in 2011 by the Food Standards Agency (FSA) found that just over three-quarters (76%) of oysters sampled from harvesting beds in UK waters tested positive for norovirus. The virus was detected at low levels in more than half (52%) of the positive samples.
Currently, these findings don't provide any greater indication of the risk of becoming ill at the point where oysters are purchased and consumed.
However, the FSA advises that older people, pregnant women, very young children and those who are unwell should avoid eating raw or lightly cooked shellfish to reduce their risk of getting food poisoning.