Infectious mononucleosis

What is infectious mononucleosis?

Infectious mononucleosis, or glandular fever, is an illness caused by a virus that infects certain blood cells. The virus is called the Epstein-Barr virus (EBV), which is a member of the herpes virus family. Typically the illness starts with a headache and fatigue, followed by a fever, sore throat and enlarged lymph glands.

The name infectious mononucleosis refers to the fact that there are increased numbers of mononuclear cells in the blood. These cells are called lymphocytes (a type of white blood cell) and fight the virus infection.

What causes glandular fever? Glandular fever is caused by exposure to the Epstein-Barr virus. It is a very common infection and most people will be exposed to it at some point in their lives.

In underdeveloped countries, exposure is more likely in early childhood. In developed countries, the age of first exposure may be delayed to older childhood and young adult age. For this reason, it is sometimes called the kissing disease. However, glandular fever is not very easy to catch (infectious). Only about 5% of people give a history of recent contact with an infected person because most people do not know that they are infected.

Who gets glandular fever and what are the risk factors?

The first infection with the EBV virus may occur during childhood, adolescence or adulthood.

About 50% of children have had this infection before the age of five years. In most of these cases, there are no clinical signs and the child is not ill.

In adolescents or adults the infection may also cause no symptoms – a so-called subclinical infection, or it may cause the recognised illness.

After the initial infection, the EBV virus remains in the body for life and is intermittently shed from the mouth, nose and throat region.

There may be reactivation of the virus which is usually subclinical. It is unclear if reactivation of EBV can cause symptoms in otherwise healthy people. It is also controversial as to whether EBV plays any role in chronic fatigue syndrome.

The EBV has been associated with African Burkitt’s Lymphoma, certain types of lymph cell cancers in people whose immune system is compromised, such as those with organ grafts or HIV. EBV is also associated with cancer of the nose and throat (nasopharyngeal cancer).

What are the symptoms and signs of glandular fever?

The four main symptoms of glandular fever are fatigue, fever, a sore throat and swollen glands, but people may have all or only some of these symptoms.

Patients usually complain of malaise (feeling unwell) with a headache and muscle aches, which lasts several days to a week, followed by fever, a sore throat and swollen glands.

The sore throat may be severe, painful and show a discharge on examination. It may look clinically like a streptococcal throat infection.

Glands anywhere in the body may be swollen, but the most common area of swelling is around the neck.

Fever usually peaks in the afternoon or early evening and fatigue is usually worse in the first two to three weeks. When fever and fatigue are the most prominent symptoms, both the onset of the illness and recovery may be much slower.

About 50% of patients have a swollen spleen and some may also have a mildly enlarged liver. Either of these can cause abdominal pain. Less common signs may be a rash, jaundice and swelling around the eyes.

How is glandular fever diagnosed?

The clinical picture of glandular fever is relatively characteristic but there is a lot of overlap with other possible illnesses. As a result, laboratory testing is generally recommended.

A blood test will confirm the diagnosis. With the test, antibodies to the Epstein-Barr virus can be detected. The body also produces T-lymphocytes to attack the EBV infected B-lymphocytes. These reactive T-lymphocytes have a characteristic appearance under the microscope and occur in large numbers in the blood of people with glandular fever.

Can glandular fever be prevented?

Infection by the Epstein-Barr virus is very common, affecting children, adolescents and adults alike. Although the virus isn’t very infectious, it is spread from person to person in the same way as influenza, in fluid from the nose and mouth. The transfer of body fluids (commonly saliva) with someone who is currently or has recently been infected with the disease should be avoided.

In rare instances, the virus has been transmitted by blood transfusion.

At present, there is no vaccine available to prevent glandular fever.

How is glandular fever treated?

The treatment is mainly aimed at relieving symptoms since there is no specific treatment for the virus. Paracetamol is preferred to aspirin for pain and fever control, because of the association between viral infections, aspirin and Reye syndrome.

People should be encouraged to rest during the acute phase of the illness, but should be up and about again once the fever, sore throat and malaise disappear.

Because there is a risk of the spleen rupturing, even if it is not enlarged, contact sports should be avoided for two months after the illness.

What is the outcome of glandular fever?

People with glandular fever usually recover without treatment. The duration of the illness is variable. The acute phase lasts about two to four weeks. People are usually able to start their normal activities after this but may find they are still tired.

Studies have shown that 20% of patients can return to school or work within one week and 50% within two weeks. Occasionally fatigue lasts for months – usually intermittently and of moderate intensity. This extended (chronic) form of the illness occurs in about 2% of patients.

Serious complications are rare but can include:

  • obstruction of the airways due to the swelling of throat tissue
  • jaundice
  • anaemia
  • bleeding due to low blood platelets
  • ruptured spleen
  • inflammation of the brain (encephalitis) or brain lining (meningitis), and various other nerve or behavioural abnormalities
When to see your doctor

Because there is no specific anti-viral treatment, people with glandular fever will recover whether treatment is given or not. However, a doctor will be able to provide a confirmed laboratory diagnosis.

If your symptoms differ from those commonly experienced with glandular fever, or last longer than four weeks, consult your doctor immediately.

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