Patient information from BMJ

Glandular fever (infectious mononucleosis)

Last published:Dec 06, 2021

Glandular fever is a common infection that usually goes away by itself without treatment.

The symptoms are often mild, although some people are more badly affected than others. And some people can be left with fatigue (tiredness) that can last for months.

What is infectious mononucleosis?

Infectious mononucleosis is the name doctors give to a group of symptoms (or 'syndrome') usually caused by infection with the Epstein Barr virus (EBV for short). It's more commonly known as glandular fever or 'mono'.

Glandular fever can also be caused by other things, including conditions that affect the body's tissues, reactions to some medicines, and cancer. But these are much less common.

EBV is often called the 'kissing' disease, as it is most commonly passed on through saliva.

Glandular fever is usually mild if you get it as a child. Many people have had glandular fever as a child without knowing what it was. You might just think you had a sore throat, swollen glands, or were a bit 'run down'.

Symptoms can be more severe as an adult, but they're still not usually serious, and the illness usually goes away by itself.

Most people who are infected with EBV never get serious symptoms. And once you are infected with EBV you carry the virus for life without any problems. Worldwide, about 90 in 100 people carry EBV.

What are the symptoms?

The main symptoms of glandular fever caused by EBV are:

• fever

• sore throat, and

• swollen glands, usually in the neck.

Some people also have a headache and aching muscles.

The symptoms of glandular fever can vary in how severe they are. They might pass in a few days or they can go on for a few weeks.

Once these main symptoms pass, you might feel very tired for weeks or even months. This might mean that you need to take a lot of time off school or work.

A few people with glandular fever develop what's called chronic fatigue syndrome (CFS). This happens when the fatigue (extreme tiredness) lasts for more than six months. In some people this chronic fatigue can last for years.

To find out more about CFS, see our leaflet on Chronic fatigue syndrome.

When glandular fever is caused by something other than EBV, the symptoms tend to be less severe. But, as with symptoms caused by EBV, they can get better quickly or can take a long time to improve.

If your symptoms are mild you probably won't need to see a doctor. But people with severe symptoms might have some tests, including a blood test, to see what has caused the illness.

Sometimes people have a scan of the abdomen. This can show if your spleen has become enlarged, which can be a symptom of severe glandular fever.

What treatments work?

Most people with glandular fever don't need any treatment, and the symptoms get better by themselves. Things you can do to feel less miserable while you recover include:

• staying hydrated: drink plenty of fluids (non-alcoholic)

• resting as much as you need to

• taking paracetamol, aspirin, or non-steroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen if you need to, for fever and pain.

But remember to never give aspirin to children, as it can cause a serious condition called Reye's syndrome.

You should also avoid strenuous physical activity and contact sports for at least several weeks after you recover. This is because exercise or injury could cause a swollen spleen to rupture.

Antibiotics will not help with glandular fever, because it is caused by a virus. Antibiotics only help with infections caused by bacteria.

Severe symptoms

Some people with glandular fever have severe symptoms, which can include trouble breathing because of swelling in the throat. If you have severe symptoms of glandular fever you need treatment in hospital.

The usual treatment is drugs called corticosteroids. These are strong anti-inflammatories that reduce swelling.

If these don't work, you might need to have a procedure to help you breathe. There are several ways of doing this, including putting a tube into your lungs, or removing swollen tonsils. But it's very rare for someone to need these treatments.

What will happen?

Most people with mild glandular fever don't even know they have had it. But if you need to see a doctor, he or she will want to follow up with you for a month or two, to make sure that you are getting better.

If you have a child or a teenager with glandular fever, you might both need to be patient: recovering completely can take a while.

The symptom that usually takes the longest to get better is the tiredness that can follow glandular fever. If it lasts for more than six months, it's classed as chronic fatigue syndrome. If this happens, talk to your doctor.

Most people recover completely from glandular fever, even if it takes a while for the fatigue to go away.

But the condition can sometimes be life threatening. This can be because of breathing problems, a ruptured spleen, or complications that affect your blood cells. But these problems are rare. Your doctor will be able to tell you if you have any of these problems and how to treat them.