Infectious Mononucleosis: Things You May Not Know

An Epstein-Barr virus infection that has an intact immune system is usually asymptomatic.
Infectious mononucleosis: things you may not know

Infectious mononucleosis is a disease produced by the Epstein-Barr virus (EBV), or the human herpes virus 4 (HHV 4).

This is a disease that is purely human. It usually affects children, teenagers and young adults.

The Epstein-Barr virus has two basic properties:

  • First, this is a virus with an affinity for B lymphocytes and oropharynx.
  • Secondly, it is a virus with the ability to remain latent (in sleep mode) and to deactivate itself when weakened by the immune system.

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

How do you get infected by it?

The infection is transmitted directly by contact with saliva of infected persons. Usually the carriers do not show any symptoms.

This is why it is often called “kissing disease”.

You can also become infected  through contact with objects such as cups or toothbrushes used by infected people. It is also possible to transmit it through blood (transfusions) or through a hematopoietic cell transplant.

Usually, the age at which you can get this disease depends on your socioeconomic level. In developing countries, this is a childhood disease. But in more developed countries, this is a common disease among teenagers.

Epstein-Barr virus infection

Epstein-Barr virus infection

Epstein-Barr virus infection in people with intact immune systems is normally asymptomatic. As a result, it goes unnoticed.

However, there are differences depending on age:

  • In childhood, the infection is mostly asymptomatic.
  • In teens and young adults, there are two possibilities. It is either asymptomatic or you suffer from infectious mononucleosis.
  • In adults over the age of 40, most of the primary cases of EBV infection result in viral hepatitis.

However, the situation is different in people with a weakened immune system (such as those with AIDS). In these cases, infection with this virus can cause lymphatic tissue disease. This can seriously ruin their lives.

Symptoms of mononucleosis


Infectious mononucleosis has an incubation period of between 4 and 6 weeks.

During these weeks, the individual usually shows flu-like symptoms (fatigue, general discomfort, low fever or fever below 38 degrees)

After this period, symptoms of infectious mononucleosis occur:

  • Very painful sore throat
  • High fever (over 40 degrees)
  • Lymph node tumor: The lymph nodes in the neck usually swell very significantly. This is one of the most characteristic signs of this disease.
  • Splenomegaly (increase in spleen size) in up to 50% of patients.
  • In some cases, the infection can cause intense fatigue (asthenia).

The presence of atypical lymphocytes and heterophilic antibodies in the blood of patients is what helps doctors diagnose the disease.


A complete diagnosis will show an increase in the presence of lymphomonocytes (over 4.5 thousand / mm3). However, this is not enough for a definitive diagnosis of infectious mononucleosis.

Lymphocytosis can be of benign origin or change when faced with an infectious or inflammatory process. It can also have a malignant origin (like what happens in leukemia).

Physicians may observe atypical or reactive lymphocytes peripheral blood distribution (visual analysis). In this case, these are different from normal lymphocytes. They are larger and have a more disorganized core. This is due to the antigenic stimulation.

This presence is an indication of how benign it is.

The fastest test to confirm the diagnosis of infectious mononucleosis is a monospot.

This is a technique that allows physicians to detect the presence of heterophile antibodies in these patients. In addition, it is negative in other cases.

Overall, this test is positive in 85% of infectious mononucleosis cases.

EBV test

Heterophilic antibodies

Heterophilic antibodies are a type of pathognomonic IgM of the Epstein-Barr virus infection. In other words, they are produced only as a result of this virus. In addition, they have the ability to collect agar platelets (Paul-Bunnell or Monospot tests).

Testing for these allows doctors to distinguish between acute and previous infections.

  • In case of an acute infection, they find Ac Anti VCA types IgM in the first place. Their presence can be detected in your blood for up to 5 months afterwards.
  • At 4 weeks from the onset of the disease, serum IgG Ac Anti VCA is displayed. However, Ac Anti-EBNA cannot be detected.
  • In case of a previous infection, they will be able to detect in the serum Ac Anti VCA and IgG Anti EBNA.

Differential diagnosis

Either way, it is important to undergo a differential diagnosis. Overall , the differential diagnosis should also be a factor in other causes of lymphocytosis, such as leukemia and lymphoma.


Patients with infectious mononucleosis treated with amoxicillin usually develop a generalized rash within three days of starting to take it. However, there is no specific therapy or treatment for infectious mononucleosis.

Complications of infectious mononucleosis

This disease can cause rupture of the spleen due to splenomegaly. However, this only happens in 1% of cases.

It can also lead to hemolytic anemia due to heterophilic antibodies that can cause lysis (destruction) of the red blood cells. Once destroyed, the bilirubin in them is released. Because of this, patients with infectious mononucleosis may show jaundice (a yellow color in the skin and mucous membranes).

Woman with fever

In addition, other symptoms that may appear are:

  • Chronic fatigue syndrome
  • Guillain-BarrĂ© syndrome
  • In patients with Duncan’s disease, who are infected with the Epstein-Barr virus, it can lead to diseases with increased lymphatic tissue mortality.

Other diseases related to EBV

In addition, there are other diseases that doctors can link to EBV:

  • Lymphoproliferative syndromes
  • Nasopharyngeal cancer (cancer of the nose and throat)
  • Systemic lupus erythematosus and other autoimmune diseases

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