Mononucleosis overview
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-In-Chief: Lakshmi Gopalakrishnan, M.B.B.S. [2]
Overview
Epstein-Barr virus, frequently referred to as EBV, is a member of the herpesvirus family and one of the most common human viruses.
Epidemiology & Demographics
- The virus occurs worldwide, and most people become infected with EBV sometime during their lives.
- In the United States, as many as 95% of adults between 35 and 40 years of age have been infected.
- Infants become susceptible to EBV as soon as maternal antibody protection (present at birth) disappears. Many children become infected with EBV, and these infections usually cause no symptoms or are indistinguishable from the other mild, brief illnesses of childhood.
- In the United States and in other developed countries, many persons are not infected with EBV in their childhood years. When infection with EBV occurs during adolescence or young adulthood, it causes infectious mononucleosis 35% to 50% of the time.
Pathophysiology
The name mononucleosis comes because the number of mononuclear leukocytes (WBCs with one-lobed nucleus) rises significantly. There are two main types of mononuclear leukocytes: monocytes and lymphocytes. Normal blood values are 35% of all white blood cells. With infectious mononucleosis, this can rise to 50-70%. Also, the total white blood count may increase to 10,000-20,000 per cubic millimeter (normally 4,000-11,000).
Cause
Epstein Barr virus is identified as the cause of infectious mononucleosis. EBV infects B-lymphocytes, producing a reactive lymphocytosis and atypical T-lymphocytes known as Downey bodies.
Diagnosis
History & Symptoms
- Symptoms of infectious mononucleosis include:
- Sometimes, a swollen spleen or liver involvement may develop.
- Heart problems or involvement of the central nervous system occurs only rarely, and infectious mononucleosis is almost never fatal.
- There are no known associations between active EBV infection and problems during pregnancy, such as miscarriages or birth defects.
Prognosis
- Although the symptoms of infectious mononucleosis usually resolve in 1 or 2 months, EBV remains dormant or latent in a few cells in the throat and blood for the rest of the person's life. Periodically, the virus can reactivate and is commonly found in the saliva of infected persons. This reactivation usually occurs without symptoms of illness.
- EBV also establishes a lifelong dormant infection in some cells of the body's immune system. A late event in a very few carriers of this virus is the emergence of Burkitt's lymphoma and nasopharyngeal carcinoma, two rare cancers that are not normally found in the United States. EBV appears to play an important role in these malignancies, but is probably not the sole cause of disease.