Norovirus and immunodeficiency

This article provides some basic information about norovirus, including how it may affect some PID patients and tips on the best ways to prevent it.

What is norovirus?

Norovirus is a common infection that causes diarrhoea and vomiting. It is often referred to as the ‘winter vomiting bug’. Most people recover within a day or two but symptoms frequently last up to five days. In the young, elderly or people with weakened immune systems, norovirus can last longer and it is easy to get dehydrated, so it is important to drink plenty of fluids to prevent this.  

How is it spread?

Norovirus is highly contagious and is easily passed from person to person as it is transmitted by touching hands or surfaces that the virus has landed on. Because of this, outbreaks can occur in places where lots of people share living spaces and toilets – especially hospitals, care homes and cruise ships! When an outbreak occurs in a hospital the affected wards have to be closed until the spate of infection is over, and this adds to the ‘winter pressure’ on health systems.

Protecting yourself against norovirus

One of the best ways to protect against norovirus and to help prevent infection is by practising good hygiene. This includes thorough hand washing with soap and warm water, especially after using the toilet and before eating or preparing food. Please note that alcohol-based gel alone probably won’t kill norovirus, so it is best to use soap and water.

Avoiding the spread of the virus

If you have been infected by norovirus, then practising good hygiene is essential to avoid the spread of the virus to others, e.g. washing your hands thoroughly with soap and warm water. Avoid visiting GP surgeries, care homes and hospitals if you have symptoms.

Those who have diarrhoea and vomiting should not prepare food until 48 hours after the symptoms have disappeared. All surfaces should be thoroughly disinfected after any episode of illness.

If possible, and you happen to have more than one toilet, we would suggest that anyone with diarrhoea and vomiting in the family uses their ‘own’ toilet and everyone else uses a different toilet until that person is better.

It is sensible to avoid contact with friends and relatives who don’t live with you if they have diarrhoea or vomiting, including for 48 hours after their symptoms have stopped. Children with diarrhoea and vomiting should also be kept away from nursery or school until 48 hours after the symptoms have stopped. If you are concerned about the risk to your children from others, check that your child’s school has a policy on this. Affected people should also stay away from swimming pools for two weeks.

As mentioned, hospitals are a particular concern, especially for those who visit regularly. Hospitals should have strict infection control procedures in place, but do ask if you’re not sure. You can help by staying at home if you develop sudden vomiting or diarrhoea, including for 48 hours after the symptoms stop. If you do need to make a hospital visit, let the doctors and nurses know in advance so that appropriate preparation can be made. Washing your hands – and checking that the staff are too! – is of key importance.

Norovirus and immunodeficiency

Many people with immune system problems who have norovirus just experience a short infection and get rid of the virus like anybody else. In fact, norovirus is so common that many people with primary or secondary immunodeficiency must have been exposed to it already. As with most other infections, immunodeficient patients might have more severe or longer-lasting symptoms, however a full recovery is the most likely outcome.

Unfortunately this doesn’t happen in everyone. A minority of people appear to be unable to clear the virus and it can stay for months, maybe years. When this happens, it is called a ‘chronic norovirus infection’.

What symptoms do these people get?

Patients affected by chronic norovirus infection mainly suffer diarrhoea that can persist for a long time. The infection reduces the surface area of the gut such that it can’t absorb nutrients very well. People then lose weight and have low levels of many important vitamins and minerals. Patients report feelings of extreme tiredness.

Which patients get chronic norovirus infection?

To date, chronic norovirus infection has been seen to affect a minority of common variable immunodeficiency (CVID) patients, often those who have a number of other complications, such as lung and liver disease. Interestingly, the patients diagnosed with norovirus sometimes already have a long-term diarrhoeal illness, which may have been labelled as ‘CVID enteropathy’. What is not clear at the moment is whether these people have underlying gut damage which makes them more vulnerable to norovirus or whether they have actually had norovirus all along.

Children with poor T cell function and especially children with severe combined immunodeficiency (SCID) are prone to norovirus infections. In these children, sometimes, the norovirus is not fully cleared until they have had a successful haematopoietic stem cell transplant (bone marrow transplant).

Research is underway to understand which specific immune problems make certain people vulnerable to chronic norovirus infection.

Treatment for norovirus infection

As yet there is nothing really proven. Viruses are difficult to treat, and there has not been much clinical (or commercial) urgency in making anti-norovirus treatments.

This is because the majority of people recover by themselves within a couple of days: by the time they got the medicine they would be better.

Doctors have therefore had to make some ‘best guesses’ at treatment. Various antiviral medications and high doses of intravenous immunoglobulin (IVIG) have been used to date. Some doctors are treating norovirus infection by putting immunoglobulins straight into the gut and other ideas include ‘sterilising’ the gut because the virus might actually need bacteria for it to cause infection.

Experimental therapies being considered include new (unlicensed) drugs and even a treatment that mimics human red blood cells and aims to act as a ‘decoy’ to get rid of the virus.

Unlike treatments, there is plenty of interest in developing a vaccine and some trials are underway. ‘Natural immunity’, that is, the immunity people get after a real infection probably only lasts about six months, even in those with healthy immune systems – and is only effective against infection with the same strain of norovirus – so it might need to be a yearly vaccine like the flu jab. As with other vaccinations, it may not really work in patients with immunodeficiency. However, if it works in everyone else and brings down the level of infection in the rest of the population, this will reduce the risk of ever encountering norovirus. Unfortunately, a vaccine may still be some way off.

How can I get tested for norovirus or find out more information?

Speak to your immunologist. Stool samples are needed to diagnose norovirus infection. However, the tests are not perfect, and if your doctor is concerned, at least three negative stool tests are needed before it is possible to say confidently that someone doesn’t have a chronic norovirus infection.

You will never be able to completely avoid norovirus. Sometimes even healthy people continue to pass the virus in their stools for weeks after they have recovered. However, the important thing to remember is that most people with immunodeficiency will not run into the problems of chronic infection.

Reviewed by Dr Matthew Buckland, Chair of PID UK’s Medical Panel. Posted November 2017