Mononucleosis overview: Difference between revisions
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==Pathophysiology== | ==Pathophysiology== | ||
*Most individuals exposed to people with infectious mononucleosis have previously been infected with [[EBV]] and are not at risk for infectious mononucleosis. | |||
*In addition, '''''transmission''''' of [[EBV]] requires intimate contact with the saliva (found in the mouth) of an infected person. Transmission of this virus through the air or blood does not normally occur. | |||
*The '''''incubation period''''', or the time from infection to appearance of symptoms, ranges from 4 to 6 weeks. Persons with infectious mononucleosis may be able to spread the infection to others for a period of weeks. However, no special precautions or isolation procedures are recommended, since the virus is also found frequently in the saliva of healthy people. | |||
*In fact, many healthy people can carry and spread the virus intermittently for life. These people are usually the primary reservoir for person-to-person transmission. For this reason, transmission of the virus is almost impossible to prevent. | |||
==Cause== | ==Cause== | ||
[[EBV|Epstein Barr virus]] | *The name '''''mononucleosis''''' comes because the number of [[white blood cells|mononuclear leukocytes]] ''(WBCs with one-lobed nucleus)'' rises significantly and is caused by [[EBV|Epstein Barr virus]]. | ||
*There are two main types of mononuclear leukocytes: [[monocyte|monocytes]] and [[lymphocyte|lymphocytes]]. Normal [[Reference_ranges_for_blood_tests#Hematology|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). | |||
*[[EBV]] infects [[B cell|B-lymphocytes]], producing a [[lymphocytosis|reactive lymphocytosis]] and [[T cell|atypical T-lymphocytes]] known as '''''Downey bodies'''''. | |||
==Diagnosis== | ==Diagnosis== | ||
Revision as of 19:00, 24 February 2012
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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
- Most individuals exposed to people with infectious mononucleosis have previously been infected with EBV and are not at risk for infectious mononucleosis.
- In addition, transmission of EBV requires intimate contact with the saliva (found in the mouth) of an infected person. Transmission of this virus through the air or blood does not normally occur.
- The incubation period, or the time from infection to appearance of symptoms, ranges from 4 to 6 weeks. Persons with infectious mononucleosis may be able to spread the infection to others for a period of weeks. However, no special precautions or isolation procedures are recommended, since the virus is also found frequently in the saliva of healthy people.
- In fact, many healthy people can carry and spread the virus intermittently for life. These people are usually the primary reservoir for person-to-person transmission. For this reason, transmission of the virus is almost impossible to prevent.
Cause
- The name mononucleosis comes because the number of mononuclear leukocytes (WBCs with one-lobed nucleus) rises significantly and is caused by Epstein Barr virus.
- 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).
- 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.