Infectious mononucleosis: what it is, how it is transmitted, and why it is dangerous

Infectious mononucleosis is a viral infection most often caused by the Epstein-Barr virus. The disease occurs most frequently in adolescents and young adults aged 15–24; it usually resolves on its own but can last for weeks. Below is what is known about transmission, duration, and consequences.

What mononucleosis is and which virus causes it

Mononucleosis (glandular fever, "kissing disease," Filatov's disease) is an acute viral illness with fever, pharyngeal involvement, enlarged lymph nodes, liver, and spleen, and characteristic blood changes. The causative agent is the DNA-containing Epstein-Barr virus of the herpesvirus family; it was isolated from Burkitt lymphoma cells in 1964. Less commonly, other viruses such as cytomegalovirus are the cause. The virus replicates in B lymphocytes: it does not kill the cells but activates their division. It is unstable in the external environment — it dies on drying, heating, and treatment with disinfectants.

How mononucleosis is transmitted

Infection occurs through saliva: during kissing, sharing dishes, utensils, and linen. Transmission through blood transfusion is possible. Outbreaks occur where people live in close quarters — in dormitories, boarding schools, camps, and kindergartens. A person is contagious for up to 7 weeks before symptoms appear and may remain contagious for several months after the illness. The virus survives outside the body for several hours. After recovery, it persists in the body for life, but this does not mean that the carrier is constantly dangerous to others.

Incubation period and main manifestations

The incubation period reaches 21 days, usually about a week. The illness can last up to two months, although the temperature usually subsides within 10 days. Onset is often gradual: fatigue, malaise, headache, then sore throat intensifies. Typical signs:

• elevated temperature, chills;
• enlarged and tender lymph nodes — most often in the neck, also in the armpits, at the elbows, and in the groin;
• severe sore throat, enlarged tonsils with a whitish-yellow coating;
• a pink rash resembling measles; it is harder to notice on dark skin;
• fatigue, drowsiness, loss of appetite, muscle pain, headache.

Less common are jaundice, chest pain, cough, photophobia, neck stiffness, and enlargement of the liver and spleen.

How infectious mononucleosis is diagnosed

The doctor performs an examination: looks for enlarged lymph nodes at the front and back of the neck, coating on the tonsils, rash, and enlarged liver and spleen. The diagnosis is confirmed by blood tests: a complete blood count (the white blood cell count may be above or below normal), the Monospot test, and antibody titers — these distinguish a current infection from one experienced earlier. Antibodies to the Epstein-Barr virus are checked separately, and other diseases, such as tonsillitis, are ruled out. Mononucleosis is also differentiated from HIV, diphtheria, rubella, viral hepatitis, and acute leukemia.

Consequences and complications, chronic mononucleosis

Most people recover fully. Timeline: the temperature subsides in about 10 days, lymph nodes and spleen return to normal within 4 weeks, fatigue resolves within a few weeks but may persist for 2–3 months. Splenic rupture is a rare but serious complication, so the doctor assesses the size of the spleen.

Complications are rare. They include liver involvement (hepatitis with jaundice more often in people over 35), heart and kidney involvement; blood changes, including anemia, low platelets, and sepsis; neurological problems — Guillain-Barré syndrome, meningitis, Bell's palsy; splenic rupture. With weakened immunity, a fatal outcome is possible. There are acute and chronic forms of the disease. The virus remains in the body for life; after the pronounced symptoms of the primary infection disappear, they usually do not return, and fatigue may persist from several weeks to 2–3 months.

When to see a doctor

Reasons for a visit: very high temperature, severe sore throat, enlarged lymph nodes on both sides of the neck, marked fatigue, a sore throat that does not go away. Consultation is needed if symptoms last longer than 10 days, and also with abdominal pain, temperature above 38.6 °C, severe headache, weakness in the arms or legs, or yellowing of the skin and eyes. You can return to work or school as soon as you feel better.

Mononucleosis by itself is not a reason to call an ambulance; 103/112 — if a person cannot swallow even their own saliva, is gasping for breath or cannot utter words, has developed sudden severe abdominal pain, marked weakness, or neck stiffness.

This material is for reference: it explains what happens and what examinations are performed, but does not replace a doctor's consultation — the decision on diagnosis and monitoring is made by a specialist.

This content is for reference and does not replace a doctor's consultation. Medical disclaimer