La infectious mononucleosis is a disease caused by Epstein-Barr virus. Mononucleosis mostly affects adolescents and young adults, but it can also affect children. In the latter, it is most often silent and therefore, not spotted.

La mononucleosis most often manifested by sore throat, headaches, a very great fatigue, a loss of appetite, a feeling of weakness throughout the body. The degree of fatigue, especially in the acute phase, can vary a lot from person to person. Some people who are more severely affected have to stop their activities for a few weeks. Sport is anyway, not recommended for everyone, during the acute phase, because of the risks for the spleen.

It is also called kissing disease, because most of the time, the virus is transmitted through saliva. However, kissing is far from always to be the cause (eating with the same cutlery, sharing a toothbrush, etc. can also promote the transmission of the virus, as can the droplets of saliva ejected into the air during coughing for example). In the end, sick people usually don’t know how they got the disease, but that’s not the most important thing!

See the symptoms of mononucleosis. 

What are the causes of mononucleosis?

Mononucleosis is caused by infection with Epstein-Barr virus. It is an extremely widespread virus, which is transmitted through saliva, but which does not always lead to infection. It is even harmless in the majority of cases, and “colonizes” us without even noticing it. Indeed, from the age of 5, 50% of individuals are carriers of the Epstein-Barr virus. In adulthood, the percentage is 90%. In some cases, without knowing why, the first infection with this virus causes mononucleosis.

Antibodies against this virus can be detected in the blood of these people and this protection is long-lasting. Once infected, a person keeps the virus in their body for the rest of their life, without having any symptoms. She does not have a recurrence. However, if a person later becomes immunocompromised for whatever reason, reactivation of the virus becomes possible and it can take a serious, complicated form.

How do you get mononucleosis? Is it very contagious? 

Le Epstein-Barr virus is very contagious, but still less than the common cold because it does not cause sneezing. It is transmitted by saliva, therefore by kisses, exchanges of utensils, soiled objects, or from mother to child.

An infected person is contagious from the moment she becomes infected. It is therefore during the incubation period: 4 to 6 weeks before the onset of symptoms. Once healed, the person remains contagious for several months.

The risk of contagion is however higher in the first weeks of the disease, when there is a fever and a sore throat. Moreover, parents are asked not to take their child or teenager to school during this period. In adults, sick leave may be prescribed for as long as symptoms are present.

How long does mononucleosis last?

After its introduction into the body, the virus first proliferates in the mouth. It then goes to the lymph nodes and the blood. It takes 4 to 6 weeks between the time the virus enters the body and the onset of symptoms: this is the incubation period.

Acute symptoms last 2 to 3 weeks. A state of fatigue may persist for a few months.

Most infectious mononucleosis will heal in three to five weeks, with fatigue lasting a few more weeks.

 Then, the virus remains “hidden” in the immune system without causing symptoms and without talking about it again (except in case of immunosuppression)

How to identify mononucleosis?

The doctor makes a sample secretions in the throat to distinguish the infectious mononucleosis bacterial angina (sore throat or sore throat).

Blood tests are requested to confirm the diagnosis of mononucleosis: they look for the presence of specific antibodies against Epstein Barr virus (EPV). This excludes the possibility that the symptoms are caused by another disease (cytomegalovirus or CMV infection, toxoplasmosis, etc.). This distinction is essential in pregnant women in particular: indeed, EPV is not dangerous for the fetus while CMV and the parasite responsible for toxoplasmosis are both.

The doctor also asks (via a blood test):

• a Blood Formulation Count (BFS) which makes it possible to find the transient increase in monocytic or monocyte lymphocytes
• Liver enzymes: they are readily increased, moderately.

For people who have had unprotected sex (s), it may be appropriate to also be tested for human immunodeficiency virus (HIV). This is because the first symptoms of HIV infection may resemble those of mononucleosis.

What are the potential complications ?

Although it induces the proliferation of certain blood cells, the mononucleosis is a disease benign, in the vast majority of cases. Complications are rare, but can still be very serious.

The most serious complication is ruptured spleen (small organ located in the left part of the abdomen and which plays a role in the purification of the blood). The infection can cause the spleen to swell (splenomegaly). This can then rupture spontaneously or after a shock, even slight. It rarely happens (0,5% to 1% of cases)², but the risk is real. This is why demanding sports and contact sports are contraindicated for people who have the mononucleosis . When the spleen is swollen, a sharp pain localized at the top and to the left of the abdomen is then felt. This situation requires urgent care. Ruptured spleen causes bleeding into the abdominal cavity and pain throughout the abdomen. It can be fatal and surgery is required.

In some cases, the virus induces a significant increase in the volume of tonsils, which can obstruct the airways and cause great difficulty in breathing (respiratory distress).

Le liver, the nervous system and red blood cells can also be targets of complications (hepatitis, jaundice, encephalitis, meningitis, hemolytic anemia, proliferation of white blood cells, etc.).

People who are immunocompromised are at greater risk for these complications.

It is rare to hospitalize a person with infectious mononucleosis, unless there is a complication.

Other diseases associated with the Epstein-Barr virus

This virus is involved in the appearance of lymphoma of Burkitt (read the article), a type of cancer that forms in white blood cells. This lymphoma is rare in the West, but endemic in Africa. In the West, it only occurs in people with severely weakened immune systems (for example, those who have received anti-rejection drugs after an organ transplant or chemotherapy). In Asians (Southeast Asia, China), Epstein-Barr virus infection is still implicated in the cancer du nasopharynx.

See the section “How to treat mononucleosis?”

People at risk

Adolescents and young adults, although the disease can occur at any age.

Risk factors

The symptoms of mononucleosis are said to be more prominent in societies where hygiene measures are predominant. In fact, the infection is then transmitted later in life (during adolescence rather than during childhood). However, when it is contracted at a young age, the infection causes much fewer symptoms and often goes unnoticed.

Can mononucleosis be prevented?