Infectious Mononucleosis

Infectious Mononucleosis

Causative agent

Epstein-Barr virus (EBV) is the cause of heterophile-positive infectious mononucleosis (IM), which is characterized by fever, sore throat, lymphadenopathy, and atypical lymphocytosis.

These infections are most common in early childhood, with a second peak during late adolescence. By adulthood, more than 90% of individuals have been infected and have antibodies to the virus. IM is usually a disease of young adults. In lower socioeconomic groups and in areas of the world with deficient standards of hygiene .


EBV is spread by contact with oral secretions. The virus is frequently transmitted from asymptomatic adults to infants and among young adults by transfer of saliva during kissing. The incubation period for IM in young adults is 4–6 weeks


  • Pharyngitis
  • Tonsillitis
  • Fever
  • Fatigue,
  • Myalgia, and malaise
  • Lymphadenopathy
  • Splenomegaly
  • Abdominal pain, nausea, or vomiting


  • Meningitis and encephalitis
  • Autoimmune hemolytic anemia
  • Red-cell aplasia, severe granulocytopenia, thrombocytopenia, pancytopenia
  • Hypertrophy of lymphoid tissue in the tonsils or adenoids can result in upper-airway obstruction, as can inflammation and edema of the epiglottis, pharynx, or uvula


EBV is transmitted by salivary secretions. The virus infects the epithelium of the oropharynx and the salivary glands and is shed from these cells. While B cells may become infected after contact with epithelial cells, studies suggest that lymphocytes in the tonsillar crypts can be infected directly. The virus then spreads through the bloodstream. The proliferation and expansion of EBV-infected B cells along with reactive T cells during IM result in enlargement of lymphoid tissue. Polyclonal activation of B cells leads to the production of antibodies to host-cell and viral proteins. During the acute phase of IM, up to 1 in every 100 B cells in the peripheral blood is infected by EBV; after recovery, 1–50 in every 1 million B cells is infected


Blood CBC

Heterophile antibodies

IgM and IgG antibodies to viral capsid antigen (VCA)





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