Mononucleosis: Surprising Things You May Not Have Known

Mononucleosis is a disease caused by Epstein-Barr virus (EBV) or human herpesvirus 4 (HHV4). The disease only occurs in humans, usually children, adolescents, and young adults.

The Epstein-Barr virus has two basic features:

• It is a virus that tends to target B lymphocytes and the pharynx.
• The virus is able to remain latent (dormant) and inactivate when the immune system is weakened.

In this article, we take a closer look at this virus.

How is mononucleosis transmitted?

It is transmitted directly through the saliva of people who carry the virus. Carriers of the virus usually do not show any symptoms, which is why the disease is often referred to as “pus disease”.

Infection can also be contracted through objects used by people carrying the virus, such as cups and toothbrushes. Infection is also possible through blood (blood transfusions) or hematopoietic stem cell transplantation.

The age at which this disease is typically acquired depends on the socioeconomic level. In developing countries, mononucleosis is a disease of children, but in more developed countries the disease is common in adolescents.

Epstein-Barr virus: infection

Epstein-Barr virus infection is usually asymptomatic in people whose immune systems are functioning normally. So it goes unnoticed.

However, here are the differences for people of different ages:

• During childhood, the infection is asymptomatic in most cases.
• There are two possibilities for adolescents and young adults: it is either asymptomatic or causes mononucleosis.
• In adults over the age of 40, most of the primary infections with this virus lead to viral hepatitis.

The situation is different in people with a weakened immune system (such as AIDS patients). In these people, this viral infection can cause lymphoid diseases that can be life-threatening.

Symptoms of mononucleosis

The incubation period for mononucleosis is 4-6 weeks. During these weeks, the infected person usually has flu-like symptoms (fatigue, general malaise, mild warming, ie fever below 38 ºC).

The following symptoms of mononucleosis appear:

• Very painful pharyngitis
• High fever (above 38 ºC)
• Clear enlargement of the lymph nodes in the neck. This is a typical symptom of the disease.

• Splenomegaly, or enlargement of the spleen, in most cases, and hepatosplenomegaly, or enlargement of the liver and spleen, in up to half of the patients.
• In some cases, the disease can cause severe weakness (asthenia).

Abnormal lymphocytes and heterophilic antibodies in a patient’s blood help doctors diagnose the disease.

Diagnosis

An increased number of monocytes (more than 4.5 thousand / mm³) can be seen in the patient’s blood. However, this is not yet sufficient to diagnose mononucleosis.

The reason for the increase in lymphocyte count may be benign, i.e. it is due to infection. The cause can also be malignant (such as leukemia).

Atypical or reactive lymphocytes can be detected in a blood sample that differ from normal lymphocytes in that they are larger and have a more disorganized nucleus due to antigen stimulation. This is a sign that this is a benign change.

The fastest way to confirm a diagnosis is the Monospot test. This method allows physicians to detect the presence of heterophilic antibodies in patients with mononucleosis. In other cases, the test result is negative.

The result of this test is generally positive in 85% of mononucleosis cases.

Heterophilic antibodies

Heterophilic antibodies are of the IgM class, typical of Epstein-Barr virus. In other words, they only arise in this viral infection. In addition, they have the ability to agglutinate red blood cells in sheep (Paul-Bunnell test or Monospot test).

These tests allow doctors to distinguish between acute and past infections.

• First, IgM class VCA antibodies are found in acute infection. Their presence can be detected in the serum up to 5 months after infection.
• At 4 weeks after the onset of the disease, IgG class VCA antibodies appear in the serum. No EBNA antibodies are detected at this stage.
• In the case of past infection, VCA IgG and EBNA IgG antibodies may be detected in the serum.

Differential diagnosis

Differential diagnosis is important to make in all cases. In general, differential diagnosis should also be made for other causes of lymphocytosis, such as leukemia and lymph node cancer.

Care

There is no cure for mononucleosis. Amoxicillin can sometimes be prescribed. Patients who eat amoxicillin usually develop a rash three days after starting treatment.

Complications of mononucleosis

Mononucleosis can cause splenic rupture as a result of splenomegaly. However, this occurs in only 1% of cases.

Mononucleosis can also lead to hemolytic anemia, as heterophilic antibodies can cause red blood cell destruction. When destroyed, the bilirubin they contain is released, which is why patients with mononucleosis may develop jaundice (yellowing of the skin and mucous membranes).

The following may also occur:

• Chronic fatigue syndrome
• Guillain-Barré syndrome
• In patients with Duncan’s syndrome, the Epstein-Barr virus can cause lymphoid diseases with an increased risk of mortality.

Other Epstein-Barr virus-related diseases

Other diseases may also be associated with EBV:

• Lymphoproliferative syndromes
• Nasal and throat cancer
• Systemic lupus erythematosus and other autoimmune diseases