INFECTIOUS MONONUCLEOSIS


I. Microbiology

  1. Caused by Epstein-Barr virus (EBV), a double-stranded DNA herpes virus
  2. Transmitted primarily by saliva
  3. Incubation period 4 to 6 weeks.
  4. Similar clinical features can be caused by infection with cytomegalovirus, adenovirus and Toxoplasma gondii

II. Diagnosis

  1. Often a clinical diagnosis
  2. Viral titers are highly specific but require acute and convalescent measurements to confirm acute infection
  3. Heterophile antibody test ("Monospot") is rapid and fairly specific for acute EBV-Makes use of the fact that the serum of a patient with acute EBV infection cuases sheep red blood cells to agglutinate. Elevated in initial weeks of illness and decline rapidly after the fourth week. False-negative in 10-15% pts, particularly in early days of illness.  Also less sensitive in children <12 years old c/w with older pts (25-50% versus 71-91%).
  4. Viral capsid antibody immunoglobulins (VCA-IgG and VCA-IgM)-More sensitive than the Monospot, so often used when clinical suspicion is high but Monospot is negative.  97% sensitive and 94% specific for the diagnosis of acute EBV infection.. VCA-IgM appears early and disappears by 6 weeks; VCA-IgG peaks at 2-4 weeks and remains positive throughout life.
  5. IgG antibodies to early antigen (EA) may indicate active infection though nonspecific
  6. Epstein-Barr nuclear antibody (EBNA)-Turns positive only 6-8wks after initial infection, so can help differentiate acute vs,  remote infection

III. Clinical features and epidemiology

  1. 95% of U.S. residents 35-40yo have serologic evidence of prior infection
  2. Peak incidence in developed is from 17-25yo; rare after 40yo
  3. Children with EBV may have milder "viral syndrome"-type illnesses; risk of complications is higher in pts > 40yo
  4. Typical presentation includes sore throat, fever, cervical lymphadenopathy, splenomegaly (with tenderness), hepatomegaly and lymphocytosis (often with "atypical" lymphocytes).
  5. Generally self-limited (4-8wks), particularly in young, healthy patients
  6. 50% of pts with acute EBV infection have liver transaminase abnormalities
  7. Other potential complications:
    1. Hemolytic anemia
    2. Thrombocytopenia
    3. Granulocytopenia
    4. Splenic rupture
    5. Encephalitis
    6. Cranial nerve palsy
    7. Guillain-Barré syndrome
    8. Pericarditis
    9. Hepatic failure
    10. Renal failure
    11. Chronic dormant EBV infection, associated with Burkitt’s lymphoma and nasopharyngeal carcinoma.

IV. Management

  1. Generally just supportive
  2. Avoid contact/collision sports/activities until asymptomatic; at least 1mo after onset of symptoms
  3. Prednisone 1mg/kg/d for short couses may help reduce tonsillar swelling if it becomes obstructive
  4. Systemic steroids are also sometimes used if serious hematologic complications (see above) ensue
  5. No antivirals shown to be effective as of 2011

(Sources include Core Content Review of Family Medicine, 2012)