EBV-positive sera (2)

Epstein-Barr virus is found throughout the world.  Its ability to cause a variety of diseases is associated with various environmental, socioeconomic, and genetic factors, some of which are discussed below.  EBV causes acute infectious mononucleosis and several oncogenic states.  An examination of Burkitt's lymphoma, nasopharyngeal carcinoma, and several lymphomas caused by general immune suppression, such as those in association with AIDS, follow this brief introduction.  EBV is also present in about 50% of Hodgkin's lymphomas, a rare disease accounting for about 1% of all U.S. malignancies (3).

Mononucleosis

The definition for infectious mononucleosis, as used by epidemiologists is: "an acute fibrile illness involving children and young adults characterized clinically by sore throat and lymphadenopathy, hematologically by lymphocytosis of 50% or more, of which 10% or more are atypical, and serologically by an elevated absorbed heterophil antibody titer and the development of EBV immunoglobulin M (IgM) and other EBV antibodies" (1).  See infection/diagnosis section for clinical tests for mononucleosis. The fact that the virus stays in the host's throat is beneficial to its transmission.  In addition, it will shed virus into the saliva for months or years after infectious mononucleosis has been cleared. (1)

Morbidity
Infectious mononucleosis is not a reported disease in most states and most countries.  It is reportable in the state of Connecticut and most morbidity data is collected from surveys of target groups such as college students (1).

Descriptive Epidemiology
Infection by EBV is more common in developing countries where sanitation, hygiene, and cooking are not as sterile as in nations such as the US.  Pre chewed food and shared saliva lead to a much higher incidence of infection than in the US, where shared saliva is characteristic of sexual activity in adolescence and early adulthood.  Interestingly, the patterns of clinical pathology are reversed.  Infants and young children do not usually get infectious mononucleosis but will test positive for anti EBV antibody.  However, the highest rate of infectious disease occurs in older children and young adults, especially college students.  The reason for this observation are not understood (1).  A study of children by Henle and Henle concluded: "It is likely, therefore, that primary infections with EBV in childhood either remain silent or are accompanied merely by mild signs and symptoms in the throat and respiratory tract" (2).

Distribution
EBV infection is worldwide.  Even remote populations such as isolated tribes in Alaska and Brazil have shown antibody reactions to EBV antigens.  Infection occurs early in life in most developing countries and usually without clinical symptoms.  In China, almost 80% were positive for EBV within their first year of life (1).  Compare this to studies at Yale, where almost 50% of students were susceptible when they entered college at an average age of eighteen years old.  Mono is mainly a disease of college students, white collar workers, and military personnel, who are able to avoid infection until adult life because of socioeconomic status.  EBV does not discriminate between the sexes or among racial groups.
 

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