Norovirus is an extremely common problem, affecting at least six hundred eighty-five million people per year.¹ It is more common in the winter months and can cause many symptoms, though it usually starts to get better within two days of the symptoms starting, and most people who have Norovirus do not need to see a doctor as it improves by itself.^2,3

This article will cover Norovirus and the ways it can be diagnosed in detail.

Introduction

Norovirus has existed since 1968 when the first outbreak happened at an Ohio school, though it has since become a worldwide issue.¹ It causes gastroenteritis, or “stomach flu”, and can make people feel extremely unwell.¹

What are the Symptoms of Norovirus?

Norovirus can cause many symptoms. These include:^1,2 

• Nausea (feeling like you are going to be sick)
• Diarrhoea
• Vomiting (throwing up)
• Aching limbs (dull pain in your arms and legs)
• A high temperature
• Headache
• Pain in the stomach

These symptoms usually start within twelve hours to two days after you are in touch with the virus, and they normally start getting better after two days of illness.¹

What is the Cause of Norovirus?

Norovirus is caused by a virus with the scientific name of Caliciviridae Viruses.¹ When you are infected with this virus, your stomach and intestines become swollen and irritated (inflamed) as a result, and this inflammation is called Gastroenteritis.¹

How does Norovirus Spread?

Norovirus is extremely contagious, meaning it can spread from one person to another very easily.² 

You can catch Norovirus by: ²

• Eating food that’s come into contact with someone who has Norovirus
• Being close to someone who has Norovirus
• Touching something that someone with Norovirus has touched and then touching your face
• Eating foods that naturally have Norovirus (some seafood, like oysters, can have Norovirus in them without being touched by a person with the illness)

The best thing to do to stop Norovirus from spreading is to wash your hands often with soap and water (hand sanitisers, like alcohol gels, do not kill Norovirus).²

Who is at Risk of Norovirus?

If you have been around people with Norovirus or have eaten food that’s been touched by someone with Norovirus, you are at risk of catching the virus.¹

If you visit somewhere where there are lots of people in a small area, this makes it more likely that you will catch Norovirus.⁴ This can be places like a school or nursery, a nursing home or a cruise ship.⁴

What to do if you have Norovirus?

If you think that you have Norovirus, you should not attend work or school due to the risk of passing it on to other people.² You should stay home until it has been at least two days since your last bout of vomiting and/or diarrhoea.²

People with Norovirus should rest and make sure they stay hydrated, preferably with water, but oral rehydration packets, sports drinks and broth are also good ways of making sure you are taking in enough fluids.⁵ Avoid drinks with lots of sugar (like fizzy pop and some fruit juices), alcohol and drinks that have caffeine (coca cola, coffee and tea) as these can make diarrhoea worse.⁵

If you are feeling like you are going to be sick, it is best to eat small amounts of food often rather than a big meal.⁵ Try to eat things that are plain and easy to digest, for example, crackers.⁵ Try to avoid food that is highly seasoned, nicotine, dairy products and fatty foods for several days.⁵

Remember to avoid contact with other people as much as possible while you are ill.⁵ Wash your hands regularly, use disinfectant wipes to clean things like door handles, and do not touch any food that anyone else may eat.⁵

When to Seek Help?

You should call 111 if:²

• There is vomiting lasting for more than two days
• There is diarrhoea lasting for more than seven days
• You are worried about a child who is less than one year old
• If there is blood in the diarrhoea
• If your child stops feeding (from either breast or bottle) while ill
• If there is bleeding from the bottom
• If there are signs of dehydration in the infected person
• If the person is sick so much that they cannot keep fluids down
• If the infected person still seems dehydrated after using rehydration sachets

You should go to A&E if:²

• If the affected person is vomiting blood
• If there is severe stomach pain that comes on suddenly
• If there is a sudden severe headache
• If an adult starts to vomit green
• If there is a green or yellow-green colour to a child’s vomit
• If the person complains of pain when looking at bright lights and has a stiff neck 
• If someone’s vomit looks like ground coffee
• If you think the person may have swallowed something poisonous

Diagnosis of Norovirus

Norovirus does not normally need help from a doctor. However, some people (for example, people whose immune system does not work very well) may need to be diagnosed so that they can be treated.¹ If your healthcare team need to investigate, there are tests that they can do to try to confirm if the problem you are having is due to Norovirus.

Speaking to your Doctor

Your doctor will ask you about your symptoms, how long you have had them, how severe they are and your general health to try to work out if the problem you have may be caused by Norovirus.⁵ 

Stool Sample

If your doctor wants more confirmation that Norovirus is the cause of your symptoms, they may ask you for a stool sample.¹ This means that they will ask you to provide some of your poo so that it can be tested in a laboratory so that your health team can check what is causing the symptoms.⁶ Your doctor will tell you what to do when you need to give a stool sample.⁶

You can collect the sample at home.⁶ You urinate (should do a wee) first so that the poo does not have any urine mixed in with it.⁶ You should put something in the toilet, like a layer of clingfilm, to catch the poo so that it does not touch the side of the lavatory or the water.⁶ Using a disposable scoop, take some of your poo and place it in the container that your doctor will provide. Pass this on to your healthcare team in the way they have asked you to.⁶

There are different ways of testing stool samples to find out if Norovirus is present. These are listed below.

Polymerase Chain Reaction

This is a way of testing samples. It involves making millions, or even billions, of copies of DNA present in a sample so that this DNA can be studied.⁷

DNA is the information that is passed down from parents to children that tells your body how to function.⁸ 

In a Polymerase Chain Reaction, the DNA of any germs in the sample is copied and increased, which makes it easier to find out what is causing the problem.⁹

Transmission Electron Microscopy

In Transmission Electron Microscopy, electrons (a very small particle that makes up part of an atom, the building blocks which make up everything in the universe)¹⁰ are shot at the sample, and this is used to create an image of what's inside a sample. If there is a virus inside the sample, this can be seen in the image and used to diagnose Norovirus.¹¹

Antigen ELISA

This test uses enzymes (proteins that help make chemical reactions happen within the body)¹² to pick up your body’s immune response to the germs from the sample.¹³ 

It is best to use at least two of these tests for diagnosis, as this increases the chances of the test accurately diagnosing the type of virus that is causing the patient’s symptoms.³

Conclusion

Norovirus is extremely common and can cause many symptoms that make people feel very ill. It normally improves after two days and doesn’t usually need to be seen by a doctor. However, if the symptoms are severe or the person has problems with their immune system, they may need to have a stool sample analysed for diagnosis and treatment.

If you have any symptoms listed in the ‘When to Seek Help’ section of this article, please make an appointment with your doctor.