Norovirus

What is norovirus?

Noroviruses are a group of viruses that can cause infection of the gut (intestines), called gastroenteritis. Viruses are types of germs smaller than bacteria. Gastroenteritis usually causes symptoms of being sick (vomiting) and diarrhoea, similar to stomach flu. Norovirus is the newer name given to the group of viruses that used to be known as Norwalk-like viruses and Norwalk virus. Noroviruses are also known as small round-structured viruses (SRSVs).

How is norovirus spread?

A norovirus present in the gut (intestines) of an infected person can pass out in their diarrhoea. It is easily spread from an infected person to another by close contact. This is usually because of the virus being present on the infected person's hands after they have been to the toilet.

Objects touched by the infected person can also allow transmission of the virus through contaminated surfaces. The virus can be passed on if the infected person prepares food and someone ingests the contaminated food, or if someone drinks contaminated water.

Outbreaks of norovirus that affect many people can occur. For example, in hospitals, nursing homes, on cruise ships and in schools.

It usually takes 24-48 hours after first contact with norovirus before symptoms develop. This period is known as the incubation period for the virus.

How long is norovirus contagious?

Norovirus is most contagious from the point at which symptoms start until 48 hours after all symptoms have ended, but it may be slightly infectious for a short period of time before symptoms start and later than 48 hours after they have ended.

How do you catch norovirus?

Norovirus is the most common virus causing infection of the gut (gastroenteritis) in adults in the UK. However, norovirus infection can occur in anyone of any age. You can get norovirus infection more than once because your body is not able to maintain immunity to norovirus infection for a long time once you have had it.

Norovirus symptoms

Norovirus presents with feeling sick (nausea) or being sick (vomiting) and diarrhoea which tends to be watery. . Sometimes there are other symptoms such as:

• Temperatura alta (fiebre).

• Un dolor de cabeza.

• Aching muscles in your arms and legs.

The symptoms tend to be relatively mild and short-lived, often only lasting one to two days. However, in a few people symptoms can last longer.

If symptoms are severe, lack of fluid in the body (dehydration) can occur. You should consult a doctor quickly if you suspect that you or your child are becoming dehydrated. Mild dehydration is common and is usually easily reversed by drinking lots of water to replace the fluids.

For more information about symptoms, including signs of dehydration, see the separate leaflets called Diarrhoea and Acute diarrhoea in children.

How is norovirus diagnosed?

A sample of your stool (faeces) may be sent to the laboratory for testing during an outbreak of infection of the gut (gastroenteritis). This is to help identify the type and source of the infection. However, in most cases testing is not necessary because the treatment is usually the same for many causes of gastroenteritis.

When should I seek medical advice for norovirus?

Norovirus in children

Most young children who have infection of the gut (gastroenteritis), including gastroenteritis caused by norovirus infection, have mild symptoms which will get better within a few days. The important thing is to ensure that your child has plenty to drink. In many cases, you do not need to seek medical advice. However, you should seek medical advice in the following cases (or if there are any other symptoms that you are concerned about):

• Si su hijo es menor de 6 meses.

• Si su hijo padece alguna enfermedad subyacente (por ejemplo, problemas cardíacos o renales, diabetes, antecedentes de parto prematuro).

• Si su hijo tiene fiebre.

• If you suspect lack of fluid in the body (dehydration) is developing (see earlier).

• Si su hijo parece somnoliento o confuso.

• If your child is being sick (vomiting) a lot and unable to keep fluids down.

• Si hay sangre en su diarrea o vómito.

• Si su hijo tiene dolor de barriga (abdominal) intenso.

• If your child has a weakened immune system because of, for example, chemotherapy treatment, long-term steroid treatment, use of immunosuppressant drugs or HIV infection which is not under control with treatment.

• Norovirus infections caught abroad.

• If your child has severe symptoms, or if you feel that their condition is becoming worse.

• If your child's symptoms are not settling - for example, vomiting for more than a few days, or diarrhoea that does not start to settle after 5-7 days.

Norovirus in adults

Again, most adults who have gastroenteritis, including gastroenteritis caused by norovirus infection, have mild symptoms which will get better within a few days. The important thing is to ensure that you have plenty to drink. In many cases, you do not need to seek medical advice. However, you should seek medical advice in the following cases (or if there are any other symptoms that you are concerned about):

• Si sospecha que se está deshidratando.

• Si vomita mucho y no puede retener líquidos.

• Si tiene sangre en la diarrea o el vómito.

• Si tiene dolor abdominal intenso.

• Si tiene síntomas graves o cree que su estado empeora.

• If you have a continuing high fever.

• Si los síntomas no remiten (por ejemplo, vómitos durante más de uno o dos días, o diarrea que no empieza a remitir después de tres o cuatro días).

• Norovirus infections caught abroad.

• If you are elderly or have an underlying health problem such as diabetes, epilepsy, inflammatory bowel disease, kidney disease.

• If you have a weakened immune system because of, for example, chemotherapy treatment, long-term steroid treatment, immunosuppressant drugs or HIV infection which is not under control with treatment.

• Si está embarazada.

Norovirus treatment

There is no specific medication to treat norovirus. The aim is to make sure that you or your child have plenty of fluids to avoid lack of fluid in the body (dehydration) until their immune system has the time to clear the infection. Children with norovirus can usually be cared for at home.

Occasionally, admission to hospital is needed if symptoms are severe, or if complications develop. For further information see the separate leaflets called Diarrhoea and Acute Diarrhoea in Children.

Medication for norovirus

Antibiotic medicines are not needed to treat norovirus. It is a viral infection so antibiotics will not be effective. See the separate leaflet called Diarrhoea Medicine for further information.

Is norovirus dangerous?

Complications of norovirus infection are not very common. If they do occur, they can include the following:

Lack of fluid (dehydration) and salt (electrolyte) imbalance in your body.

This is the most common complication. It occurs if the water and salts that are lost in your stools (faeces), or when you have been sick (vomited), are not replaced by you drinking adequate fluids. If you can manage to drink plenty of fluids then dehydration is unlikely to occur, or is only likely to be mild and will soon recover as you drink. Severe dehydration can lead to a drop in your blood pressure. This can cause reduced blood flow to your vital organs. If dehydration is not treated, kidney failure may also develop.

Intolerancia a la lactosa

Lactose intolerance can sometimes occur for a period of time after norovirus infection. It is known as secondary or acquired lactose intolerance. Your gut (intestinal) lining can be damaged by the episode of infection of the gut (gastroenteritis). This leads to lack of an enzyme called lactase that is needed to help the body digest the milk sugar lactose. Lactose intolerance leads to bloating, tummy (abdominal) pain, wind and watery stools after drinking milk. The condition gets better when the infection is over and the intestinal lining heals.

Síndrome del intestino irritable

En ocasiones, el SII se desencadena por un episodio de gastroenteritis.

Persistent diarrhoeal syndromes

This may develop but is rare.

Reducción de la eficacia de algunos medicamentos

During an episode of gastroenteritis, certain medicines that you may be taking for other conditions or reasons may not be as effective. This is because the vomiting and diarrhoea mean that reduced amounts of the medicines are taken up (absorbed) into your body. Examples of such medicines are medicines for epilepsy, diabetes and contraception. Speak with your doctor or practice nurse if you are unsure of what to do if you are taking other medicines and have gastroenteritis.

Certain patients will have a list of 'sick day rules' from their GP or consultant - this includes patients with adrenal insufficiency and those taking some medications. It is important to follow this advice if you fall into one of these groups.

How to prevent the spread of norovirus

If you or your child have norovirus infection, the following are recommended to prevent the spread of infection to others:

• Washing your hands thoroughly after going to the toilet. Ideally, use liquid soap and water but any soap is better than none. Dry properly after washing. If your child wears nappies, be especially careful to wash your hands after changing nappies and before preparing, serving, or eating food.

• Si tienes que utilizar un orinal, ponte guantes para manipularlo, tira el contenido en un retrete y, a continuación, lava el orinal con agua caliente y detergente y déjalo secar.

• No compartas toallas ni franelas.

• No prepares ni sirvas comida para los demás.

• Si la ropa o la ropa de cama están sucias, primero elimine las deposiciones (heces) en el inodoro. A continuación, lávelos en otro lavabo a la temperatura más alta posible.

• Regularly clean the toilets that you use, with disinfectant such as a bleach-based household cleaner. Wipe the flush handle, toilet seat, taps, door handles, surfaces or objects with hot water and detergent at least once a day. Keep a cloth just for cleaning the toilet (or use a disposable one each time).

• Stay at home and off work, school, college, etc until at least 48 hours after the last episode of diarrhoea or being sick (vomiting). Avoid contact with other people as far as possible during this time.

• Food handlers: if you work with food and develop diarrhoea or vomiting, you must immediately leave the food-handling area. For most, no other measures are needed, other than staying away from work until at least 48 hours after the last episode of diarrhoea or vomiting. In the UK there is no need for a report from your GP to say that you are fit to return to work. If your employer wants such an assessment, they should commission it themselves from an occupational health physician.

Norovirus prevention

The advice given in the previous section is mainly aimed at preventing you or your child from spreading norovirus infection of the gut (gastroenteritis) to other people if you are infected. However, in general, good hygiene is essential to prevent the spread of many infections to others and to reduce your chance of picking up infections from others.

Handwashing or using an alcohol-based hand sanitiser is the most important thing that you and your child can do. In particular, always wash your hands and dry them thoroughly and teach children to wash and dry theirs:

• Después de ir al baño (y después de cambiar pañales o ayudar a un niño mayor a ir al baño).

• Antes de preparar o tocar alimentos o bebidas.

• Antes de comer.

If you smoke, you should also wash your hands before smoking. The simple measure of washing hands regularly and properly is known to make a big difference to the chance of developing norovirus.

Preguntas más frecuentes

Can norovirus kill you?

Norovirus is rarely deadly but can cause dehydration. Most recover in days, but young children, older adults, and vulnerable people may need medical care.

Should you eat with norovirus?

With norovirus, you should focus on keeping hydrated with fluids first. Eat bland foods, like toast or rice, once you feel ready, and avoid fatty or spicy meals until recovered.

Can you get norovirus twice?

Yes, it’s possible to catch norovirus more than once. This is because the virus comes in many different strains, and the immunity your body builds after one infection is only short-lived. Even if you’ve had norovirus before, you can still pick it up again if exposed to a different strain or after your immunity fades.

Can you have norovirus without vomiting?

Yes, you can have norovirus without vomiting. Whilst sudden vomiting is one of the most common symptoms, some people mainly experience diarrhoea, stomach cramps, fever, or body aches.