Infectious Mononucleosis

1. Clinical Overview

Summary

Infectious mononucleosis is a self-limiting lymphoproliferative disorder caused by primary infection with Epstein-Barr virus (EBV), a ubiquitous gamma-herpesvirus that establishes lifelong latency in B lymphocytes. It predominantly affects adolescents and young adults aged 15-24 years, with characteristic clinical features including fever, pharyngitis, lymphadenopathy, and fatigue. The disease is typically benign and resolves spontaneously within 2-4 weeks, though complications occur in 5-10% of cases and post-viral fatigue syndrome affects 10-20% of patients for months. EBV infection confers lifelong immunity, with over 90% of adults worldwide seropositive by age 30. Diagnosis relies on clinical presentation combined with heterophile antibody testing (Monospot) or EBV-specific serology, with management focused on supportive care and complication prevention, particularly splenic rupture which occurs in 0.1-0.5% of cases. [1,2]

Key Facts

• Causative Agent: Epstein-Barr virus (EBV/HHV-4), a double-stranded DNA gamma-herpesvirus.
• Incidence: 45-50 per 100,000 population annually in Western countries; peaks in adolescents aged 15-24.
• Incubation Period: 30-50 days (range 4-90 days), longer than most viral infections.
• Transmission: Saliva (hence "kissing disease"); also blood transfusions, organ transplantation.
• Immunity: Lifelong after primary infection; 90-95% of adults seropositive worldwide.
• Mortality: Less than 1 per 100,000; deaths from splenic rupture, airway obstruction, neurological complications.
• Economic Impact: 1-2 million work/school days lost annually in United States; significant healthcare costs.

Clinical Pearls

The "Kissing Disease": EBV is transmitted via saliva with an infectious dose as low as 200-500 viral particles, explaining high transmission rates among adolescents engaging in intimate contact. Viral shedding persists for 6-18 months post-primary infection.

Heterophile Antibodies: The Monospot test detects IgM antibodies that agglutinate sheep or horse red blood cells—a non-specific immune response to EBV B-cell infection. Sensitivity is 85-90% in adolescents/adults but only 50-70% in children under 12 years. False negatives occur in first week of illness (25-30% of cases).

Splenic Risk: Splenomegaly occurs in 50-60% of cases with peak size at 10-21 days; splenic rupture risk is 0.1-0.5% with 50% occurring spontaneously (no trauma). Contact sports should be avoided for minimum 4 weeks, with some guidelines recommending 6-8 weeks or until spleen non-palpable on examination.

Chronic Fatigue: Post-viral fatigue syndrome affects 10-20% of patients, with symptoms persisting beyond 6 months. This is distinct from chronic active EBV infection (CAEBV), a rare life-threatening disorder seen predominantly in East Asia.

Ampicillin Rash: 80-100% of patients develop a maculopapular rash when given ampicillin or amoxicillin due to transient immunological dysregulation—NOT a true penicillin allergy. Mechanism involves formation of drug-antibody complexes and enhanced T-cell reactivity against penicillin haptens during acute EBV infection.

Why This Matters Clinically

• Common Presentation: Accounts for 2-5% of all pharyngitis presentations in primary care and up to 8% in college health centers.
• Diagnostic Challenge: Atypical presentations occur in 30-40% of cases; must exclude bacterial pharyngitis, lymphoma, HIV seroconversion, CMV infection.
• Complication Prevention: Early recognition and patient education prevents splenic rupture (mortality 9-13% if ruptured), airway obstruction, and enables monitoring for rare complications.
• Public Health: Understanding transmission dynamics prevents nosocomial spread; healthcare workers with active infection should avoid patient contact.
• Long-term Associations: EBV causally linked to Burkitt's lymphoma, Hodgkin's lymphoma (40% of cases), nasopharyngeal carcinoma, post-transplant lymphoproliferative disease.
• Healthcare Burden: Average illness duration 2-4 weeks with additional 2-8 weeks convalescence; significant absenteeism from work/education.
• Antibiotic Stewardship: Proper diagnosis prevents inappropriate antibiotic prescribing for viral pharyngitis; reducing antibiotic resistance.

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2. Epidemiology

Global Burden

• Seroprevalence: 90-95% of adults worldwide EBV-seropositive by age 30-40 years; nearly 100% in developing countries by adolescence.
• Annual Incidence: 45-50 per 100,000 population in Western countries; up to 200-500 per 100,000 in college-age populations.
• Age Distribution: Bimodal—early childhood (asymptomatic) and adolescence/young adulthood (symptomatic). Peak symptomatic incidence 15-24 years; rare presentation over 40 years (5-10% of cases).
• Geographic Variation: Earlier seroconversion in developing countries (90% by age 5) vs. developed countries (40-50% by age 5); lower socioeconomic status associated with earlier infection.
• Sex Distribution: Equal infection rates; some studies suggest slightly higher symptomatic presentation in males (male:female ratio 1.2:1).
• Seasonal Pattern: Winter-spring peak in temperate climates due to increased indoor crowding; less pronounced in tropical regions.

Risk Factors and Odds Ratios

Transmission Dynamics

• Primary Mode: Saliva transmission via oral-oral contact (kissing, sharing utensils, drinks).
• Viral Load: 10^5 to 10^8 viral copies/mL in saliva during acute infection; 10^2 to 10^4 during asymptomatic shedding.
• Secondary Modes: Blood transfusions (rare with modern screening), organ transplantation, sexual contact (genital secretions).
• Incubation Period: 30-50 days (range 4-90 days); mean 40-45 days.
• Infectious Period: Peak infectivity during acute illness; viral shedding continues 6-18 months post-primary infection; lifelong intermittent reactivation with asymptomatic shedding.
• Asymptomatic Shedding: 20-30% of seropositive individuals shed virus in saliva at any given time; accounts for most transmission.
• Attack Rate: 10-30% in susceptible close contacts; higher in intimate/sexual partners.

Associated Conditions and Malignancies

• Hodgkin's Lymphoma: 2-3x increased risk; EBV genome detected in 40% of cases (Reed-Sternberg cells).
• Burkitt's Lymphoma: 95% of endemic (African) cases EBV-positive; 15-20% of sporadic cases.
• Nasopharyngeal Carcinoma: Nearly 100% of undifferentiated cases EBV-positive; endemic in Southern China, Southeast Asia.
• Multiple Sclerosis: Epidemiological association (OR 2-3); EBV seropositivity required but not sufficient.
• Chronic Active EBV (CAEBV): Rare (less than 1:1,000,000); predominantly East Asian populations; systemic illness with high EBV viral load, organ dysfunction, mortality 50-90%.
• Post-transplant Lymphoproliferative Disease (PTLD): 1-20% of transplant recipients depending on organ type and immunosuppression; highest risk lung/intestine transplants.
• X-linked Lymphoproliferative Syndrome (XLP): Fatal infectious mononucleosis in boys with SH2D1A or XIAP mutations; 75% mortality from primary EBV.

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3. Pathophysiology

Molecular Virology

Viral Structure:

• Genome: Linear double-stranded DNA, 172 kilobase pairs encoding ~85 genes.
• Family: Herpesviridae, subfamily Gammaherpesvirinae (γ-herpesvirus).
• Tropism: Primary B lymphocytes (CD21+ cells) and oropharyngeal epithelium.
• Latency Programs: Type 0, I, II, III latency with differential viral gene expression; Type III drives B-cell proliferation in primary infection.

Exam Detail: Viral Entry Mechanism:

1. Epithelial Cell Entry: EBV glycoprotein BMRF2 binds to integrins, allowing epithelial cell infection and lytic replication.
2. B-Cell Entry: EBV glycoprotein gp350 binds CD21 (complement receptor 2/CR2) on B cells; gp42 interacts with MHC class II for membrane fusion.
3. Nuclear Transport: Viral capsid transported to nucleus; circular episomal DNA established.
4. Latency Establishment: Expression of EBV nuclear antigens (EBNA1-6) and latent membrane proteins (LMP1, LMP2) drives B-cell immortalization.

Immune Evasion:

• MHC Class I Downregulation: BNLF2a protein blocks TAP transporter, reducing antigen presentation.
• Apoptosis Inhibition: LMP1 upregulates Bcl-2, preventing infected cell death.
• Complement Resistance: CD21 binding confers complement resistance.
• Cytokine Mimicry: EBV IL-10 homolog (vIL-10) suppresses Th1 responses and cytotoxic T cells.

Step 1: Viral Entry and Primary Infection

Oropharyngeal Phase (Days 0-7):

• Site: Epithelial cells of oropharynx, salivary glands, tonsils.
• Process: Lytic replication produces 10^5-10^8 viral particles; epithelial cells lyse, releasing virus into saliva.
• B-Cell Infection: Virus crosses epithelial barrier, infects naive B cells in tonsillar crypts via CD21 receptor.
• Latency Induction: Type III latency program initiated; all latent genes expressed (EBNA1-6, LMP1/2).
• Polyclonal B-Cell Activation: Latent proteins mimic normal B-cell activation signals (CD40, BCR); drives proliferation.

Step 2: Immune Response Activation

Innate Immunity (Days 4-10):

• NK Cells: Early responders; lyse EBV-infected B cells via NKG2D activation.
• Interferons: Type I interferons (IFN-α/β) produced; limit viral replication and spread.
• Macrophages: Activated by viral PAMPs; phagocytose infected cells and debris.

Adaptive Immunity (Days 7-21):

• CD8+ Cytotoxic T Cells: Massive expansion (up to 40-50% of circulating lymphocytes); recognize viral peptides on MHC class I.
• Atypical Lymphocytes: Activated CD8+ T cells with abundant cytoplasm, irregular nuclei (Downey cells); NOT infected B cells but reactive T cells.
• CD4+ Helper T Cells: Provide help for B-cell antibody production and CD8+ T-cell activation.
• Antibody Response:
  • "VCA IgM: Appears day 7-10, peaks 2-4 weeks, declines by 3 months."
  • "VCA IgG: Appears day 10-14, persists lifelong."
  • "EBNA IgG: Delayed appearance (3-12 weeks), persists lifelong; indicates past infection."
  • "EA (early antigen) IgG: Variable; may indicate reactivation if present alone."

Cytokine Storm:

• Pro-inflammatory: TNF-α, IFN-γ, IL-6, IL-1β released by T cells and macrophages.
• Clinical Manifestations: Fever (IL-1β, IL-6, TNF-α), fatigue (IFN-γ), lymphadenopathy (lymphocyte infiltration).
• Immunoregulation: IL-10, TGF-β produced to limit inflammation; balance determines symptom severity.

Step 3: Lymphoproliferative Response

B-Cell Expansion:

• Mechanism: EBV-infected B cells proliferate unchecked initially due to LMP1-mediated growth signals.
• Polyclonal Activation: Non-specific B-cell activation leads to heterophile antibody production (anti-sheep/horse RBC).
• T-Cell Control: CD8+ T cells recognize EBNA3 antigens, target infected B cells for destruction.

Splenomegaly (50-60% of cases):

• Pathology: Reactive lymphoid hyperplasia; white pulp expansion with lymphocyte infiltration.
• Peak Size: Day 10-21 of illness; can increase splenic volume 2-3 fold.
• Capsular Tension: Increased intrasplenic pressure; subcapsular hematomas develop in 30%; rupture risk 0.1-0.5%.
• Histology: Lymphocytic infiltration of red pulp, white pulp hyperplasia, immunoblasts in sinusoids.

Hepatomegaly (10-20% of cases):

• Mechanism: Portal tract lymphocytic infiltration; hepatocyte injury from cytokine-mediated inflammation.
• Biochemistry: Mild transaminitis (ALT/AST 2-5x ULN) in 80-90%; cholestasis rare (ALP elevation 10-20%).
• Histology: Lymphocytes in portal triads, sinusoids; rare hepatocyte necrosis; no chronic fibrosis.

Step 4: Organ System Involvement

Pharyngitis:

• Mechanism: Direct epithelial cell infection and lysis; cytokine-mediated inflammation; secondary bacterial colonization.
• Exudate: Fibrinous exudate from neutrophil and macrophage infiltration; may mimic Group A Streptococcus.
• Palatal Petechiae: Capillary fragility from thrombocytopenia and cytokine effects; occurs in 25-30% of cases.

Lymphadenopathy:

• Distribution: Generalized but most prominent in posterior cervical chain (80-90%), anterior cervical (70%), axillary (40%), inguinal (30%).
• Histology: Follicular hyperplasia, immunoblastic proliferation, Reed-Sternberg-like cells (benign; do not indicate Hodgkin's).
• Size: Typically 1-3 cm; tender, rubbery, mobile; matted nodes rare (suggests bacterial or malignant process).

Hematological Changes:

• Lymphocytosis: Absolute lymphocyte count > 4.5 x 10^9/L in 70-80%; > 50% lymphocytes typical.
• Atypical Lymphocytes: > 10% of WBC (diagnostic threshold); represent activated CD8+ T cells attacking EBV-infected B cells.
• Thrombocytopenia: Mild (100-150 x 10^9/L) in 25-50%; severe (less than 20 x 10^9/L) in 1-2%; mechanism is immune-mediated platelet destruction.
• Mild Anemia: Normocytic anemia in 10-20%; hemolysis rare (cold agglutinin disease, 0.5-3%).

Step 5: Resolution and Latency

Immune Control (Weeks 2-4):

• CD8+ Expansion: EBV-specific CD8+ T cells reach 0.5-5% of total T cells (vs. 0.01-0.1% for other viruses).
• B-Cell Clearance: Infected lytic B cells eliminated; only latently infected memory B cells survive.
• Symptom Resolution: Cytokine levels normalize; lymphoid hyperplasia regresses.

Latent State:

• Reservoir: Resting memory B cells harbor EBV as circular episomal DNA; 1-50 infected cells per million B cells.
• Latency Type 0/I: Minimal viral gene expression (EBNA1 only or none); evades immune detection.
• Lifelong Persistence: EBV remains in host for life; reactivation suppressed by memory CD8+ T cells.

Periodic Reactivation:

• Triggers: Stress, immunosuppression, concurrent infection.
• Lytic Cycle: Oropharyngeal epithelial cells support lytic replication; virus shed in saliva.
• Asymptomatic: Immune memory rapidly controls reactivation; no symptoms in immunocompetent hosts.

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4. Clinical Presentation

Classic Triad (Present in 60-80% of Cases)

• Fever: High-grade (> 38.5°C, often 39-40°C), sustained or remittent, lasting 1-3 weeks; antipyretics provide limited relief.
• Pharyngitis: Severe sore throat with tonsillar enlargement, erythema, white/gray exudate; often most prominent symptom; difficulty swallowing (odynophagia).
• Lymphadenopathy: Generalized but most prominent posterior cervical chain; tender, bilateral, mobile nodes 1-3 cm; may persist 4-6 weeks.

Symptoms by Frequency and Timeline

Signs and Examination Findings

General Examination:

• Fever: Often > 39°C (102°F); tachycardia proportional to temperature.
• Fatigue: Marked lethargy; reduced functional status; may be bedridden in severe cases.
• Rash:
  • "Spontaneous: Maculopapular, morbilliform in 10-15%; trunk and extremities; transient (3-7 days)."
  • "Ampicillin-induced: Maculopapular, pruritic in 80-100% if given ampicillin/amoxicillin; NOT a true drug allergy; appears day 7-10 after antibiotic initiation."

Head and Neck Examination:

• Pharyngitis: Tonsillar enlargement (grade 2-4), erythema, white/gray exudate (50-70%); may meet in midline (grade 4, "kissing tonsils"); differentiation from streptococcal pharyngitis difficult clinically.
• Palatal Petechiae: 25-30% of cases; at junction of hard and soft palate; highly suggestive of EBV (vs. bacterial).
• Periorbital Edema: 10-30% of cases; may give "Hoagland sign" appearance; mechanism unclear, possibly cytokine-mediated.
• Lymphadenopathy:
  • "Posterior cervical: 80-90% (most characteristic finding)."
  • "Anterior cervical: 70-80%."
  • "Submandibular: 60-70%."
  • "Axillary: 30-40%."
  • "Inguinal: 20-30%."
  • "Characteristics: Tender, mobile, rubbery, 1-3 cm; matting suggests bacterial superinfection or alternative diagnosis."

Abdominal Examination:

• Splenomegaly: 50-60% of cases; palpable 2-4 cm below left costal margin; peak size day 10-21; tender on palpation suggests capsular distension or subcapsular hematoma.
• Hepatomegaly: 10-20% of cases; 2-3 cm below right costal margin; mild tenderness; massive hepatomegaly rare (suggests alternative diagnosis).
• Abdominal Tenderness: Left upper quadrant tenderness over spleen; peritoneal signs suggest rupture (surgical emergency).

Other Systems:

• Jaundice: 5-10% develop visible icterus; reflects cholestatic hepatitis; rarely severe.
• Petechiae/Purpura: 5-10%; from thrombocytopenia; palatal most common; widespread suggests severe thrombocytopenia or ITP.
• Cardiovascular: Usually normal; myocarditis rare (0.1-0.5%); pericarditis very rare.
• Respiratory: Usually normal; inspiratory stridor suggests airway obstruction from tonsillar hypertrophy (1-2%, emergency).
• Neurological: Usually normal; meningism in aseptic meningitis (0.5-1%); focal signs suggest encephalitis or Guillain-Barré syndrome.

Atypical Presentations

By Age:

• Young Children (less than 5 years): Often asymptomatic (50-70%) or mild URI symptoms; pharyngitis less prominent; heterophile antibodies often negative.
• Older Adults (> 40 years): Jaundice more common (15-20%); fever may be prolonged (> 3 weeks); hepatitis more severe; lymphadenopathy less prominent.
• Elderly (> 60 years): Atypical presentations common (40-50%); fever of unknown origin; minimal pharyngitis; consider alternative diagnoses.

Specific Presentations:

• Chronic Active EBV (CAEBV): Persistent/recurrent symptoms > 6 months; fever, lymphadenopathy, hepatosplenomegaly; high EBV viral load (> 10^3-10^4 copies/μg DNA); organ dysfunction; life-threatening; predominantly East Asian populations; mortality 50-90% over 5 years without hematopoietic stem cell transplant.
• Severe Pharyngitis: Exudate so severe it mimics diphtheria or bacterial abscess; may cause airway obstruction.
• Hepatitic Presentation: Predominant jaundice, transaminitis (ALT/AST > 1000 U/L), hepatomegaly; may mimic acute viral hepatitis A/B.
• Neurological: Encephalitis (0.5-1%), aseptic meningitis (0.5-1%), Guillain-Barré syndrome (0.1-0.5%), transverse myelitis (rare), cranial nerve palsies (especially VII).
• Hematological: Severe thrombocytopenia (less than 20 x 10^9/L) in 1-2%; autoimmune hemolytic anemia (2-3%); hemophagocytic lymphohistiocytosis (HLH, less than 0.5%); aplastic anemia (very rare).

Red Flags for Complications

Immediate Life-Threatening (Call 911/999):

1. Severe Abdominal Pain: Sudden, severe LUQ pain with shoulder tip pain (Kehr's sign) suggests splenic rupture; hypotension, tachycardia indicate hemorrhagic shock.
2. Respiratory Distress: Inspiratory stridor, dyspnea, drooling, inability to swallow secretions suggest airway obstruction from tonsillar hypertrophy; medical emergency.
3. Altered Consciousness: Confusion, seizures, focal neurological signs suggest encephalitis, meningitis, or cerebrovascular complications.
4. Severe Bleeding: Widespread purpura, mucosal bleeding, hematemesis from severe thrombocytopenia or DIC.

Urgent (Same-Day Evaluation): 5. Persistent High Fever > 3 Weeks: Consider complications (splenic abscess, secondary bacterial infection), alternative diagnoses (lymphoma, HIV), or chronic active EBV. 6. Severe Jaundice: Bilirubin > 85 μmol/L (5 mg/dL) suggests severe hepatitis; monitor for hepatic failure. 7. Pancytopenia: Suggests hemophagocytic lymphohistiocytosis, aplastic anemia, or bone marrow infiltration. 8. Immunocompromised Patient: Higher risk of severe complications, PTLD, chronic active EBV; requires specialist input.

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5. Differential Diagnosis

Must-Not-Miss Diagnoses

Common Mimics

Clinical Decision Rules

Centor Score for Streptococcal Pharyngitis:

• Tonsillar exudate: +1
• Tender anterior cervical lymphadenopathy: +1
• Fever > 38°C: +1
• Absence of cough: +1
• Score ≥3: Consider strep test; BUT in IM, Centor often ≥3, leading to inappropriate antibiotics
• Caveat: Splenomegaly, posterior cervical nodes, atypical lymphocytes NOT part of strep pharyngitis

Heterophile Test Interpretation:

• Positive: Infectious mononucleosis very likely (specificity 95-99%).
• Negative in first week: Repeat in 7-10 days if clinical suspicion high (sensitivity increases with time).
• Negative after 2 weeks: Consider EBV serology (VCA IgM/IgG, EBNA IgG) or alternative diagnoses (CMV, toxoplasma, HIV, lymphoma).

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6. Investigations

Diagnostic Approach

Initial Assessment (All Suspected Cases):

1. Full Blood Count with differential
2. Heterophile antibody test (Monospot, Paul-Bunnell)
3. Liver function tests (AST, ALT, bilirubin, ALP)
4. Throat swab if bacterial pharyngitis cannot be excluded

If Heterophile Negative (Especially Age less than 12 or > 40): 5. EBV serology (VCA IgM, VCA IgG, EBNA IgG)

If Atypical Features or Complications: 6. EBV PCR (viral load) 7. Ultrasound abdomen (spleen size, subcapsular hematoma) 8. Additional serology (CMV, HIV, toxoplasma) as indicated

Essential Investigations

1. Full Blood Count (FBC)

Atypical Lymphocyte Morphology (Downey Cells):

• Type I: Cytoplasm pale blue, vacuolated; nucleus round; 10-20% of atypical lymphocytes.
• Type II: Cytoplasm basophilic, abundant; nucleus irregular, indented; 40-60% of atypical lymphocytes.
• Type III: Large cell, deeply basophilic cytoplasm; immature nucleus; 20-30% of atypical lymphocytes; may resemble blast cells.
• Key Point: Atypical lymphocytes are NOT infected B cells; they are activated cytotoxic CD8+ T cells responding to EBV-infected B cells.

2. Heterophile Antibody Test (Monospot, Paul-Bunnell)

Mechanism:

• Non-specific IgM antibodies produced by EBV-activated polyclonal B cells that agglutinate sheep or horse red blood cells.
• NOT directed against EBV antigens but cross-react with animal RBC antigens.

Performance Characteristics:

Timing:

• Week 1 of illness: Positive in only 60-70% (25-30% false negative rate).
• Week 2: Positive in 85-90%.
• Week 3-4: Positive in 90-95% (peak sensitivity).
• After 3 months: Declines; 50% negative by 6 months; 90% negative by 12 months.

False Negatives:

• First week of illness (most common cause).
• Age less than 12 years (heterophile antibodies develop less reliably in children).
• Immunocompromised patients.
• Some adults never develop heterophile antibodies (5-10%).

False Positives (Rare, 1-5%):

• Lymphoma (Hodgkin's, NHL)
• Systemic lupus erythematosus (SLE)
• Toxoplasmosis
• Viral hepatitis
• Malaria

Clinical Use:

• Positive result: Confirms infectious mononucleosis in appropriate clinical context (no further testing needed in typical presentation).
• Negative result in first week: Repeat in 7-10 days if clinical suspicion high.
• Persistent negative after 2 weeks: Proceed to EBV-specific serology.

3. EBV-Specific Serology

Antibodies and Interpretation:

Serological Profiles:

When to Order EBV Serology:

• Heterophile antibody negative after 2 weeks of illness.
• Age less than 12 years or > 40 years (lower heterophile sensitivity).
• Immunocompromised patients.
• Atypical presentations.
• Chronic symptoms (> 6 months) to exclude chronic active EBV.
• Pregnant women (confirm immunity status; primary infection in pregnancy has fetal risks).

4. EBV PCR (Viral Load)

Indications:

• Immunocompromised patients (transplant recipients, HIV/AIDS, chemotherapy).
• Suspected chronic active EBV (CAEBV).
• Monitoring post-transplant lymphoproliferative disease (PTLD).
• Suspected EBV-associated malignancy.

Viral Load Interpretation:

• Acute IM (immunocompetent): 10^3-10^5 copies/mL plasma; NOT routinely measured.
• Chronic Active EBV: > 10^3-10^4 copies/μg peripheral blood mononuclear cell DNA; persistently high.
• PTLD: Monitoring helps predict disease; rising levels concerning.
• Note: Viral load NOT useful for diagnosing uncomplicated IM in immunocompetent patients (serology preferred).

5. Liver Function Tests (LFTs)

Monitoring:

• Check LFTs at baseline in all patients.
• Repeat weekly if elevated to ensure normalization (usually by 4-8 weeks).
• Severe transaminitis (> 1000 U/L) or jaundice requires specialist input; exclude viral hepatitis, drug-induced liver injury.

6. Throat Swab (if Bacterial Pharyngitis Not Excluded)

Indication: Cannot reliably differentiate streptococcal from EBV pharyngitis clinically; both can have exudate, fever.

Method: Rapid antigen detection test (RADT) for Group A Streptococcus (sensitivity 85-95%, specificity > 95%); if negative and high Centor score, culture.

Result Interpretation:

• Positive: Treat for streptococcal pharyngitis (though 5-10% of IM patients have concurrent strep carriage).
• Negative: Supports viral pharyngitis; avoid antibiotics (especially ampicillin/amoxicillin).

Advanced/Specialist Investigations

7. Abdominal Ultrasound

Indications:

• Clinical splenomegaly to assess size, guide return-to-activity timing.
• Abdominal pain (assess for subcapsular hematoma, splenic infarction).
• Pre-participation clearance for athletes (ensure spleen non-palpable before contact sports).

Findings:

• Normal spleen size: less than 13 cm craniocaudal length.
• IM splenomegaly: 13-20 cm (mild-moderate), > 20 cm (massive, higher rupture risk).
• Subcapsular hematoma: Hypoechoic rim; increases rupture risk; consider admission, serial imaging.
• Splenic infarction: Wedge-shaped hypoechoic areas; abdominal pain; usually managed conservatively.

8. CT Abdomen (if Splenic Rupture Suspected)

Indications: Acute severe LUQ abdominal pain, hypotension, falling hemoglobin.

Findings:

• Splenic rupture: Capsular disruption, hemoperitoneum, splenic laceration.
• Grading: AAST grading I-V; Grade III-V usually require splenectomy.

Management: Immediate surgical consultation; resuscitation; laparotomy/splenectomy if unstable.

9. Lumbar Puncture (if Neurological Complications Suspected)

Indications: Meningism, severe headache, altered consciousness, seizures, focal neurology.

CSF Findings in EBV Aseptic Meningitis:

• Opening pressure: Normal or mildly elevated.
• WBC: 10-500 cells/μL, lymphocyte predominant.
• Protein: 0.4-1.0 g/L (mildly elevated).
• Glucose: Normal.
• EBV PCR: May be positive in CSF; confirms CNS involvement.

10. Immunological Tests

Lymphocyte Subsets (Flow Cytometry):

• CD8+ T cells: Markedly elevated (40-60% of lymphocytes); activated phenotype (CD8+HLA-DR+).
• CD4:CD8 ratio: Inverted (normal 1.5-2.0; in IM often less than 0.5).
• Indication: Atypical cases, suspected immunodeficiency, chronic active EBV.

Autoantibodies (if Autoimmune Complications):

• Cold agglutinins: Positive in 50-70% of IM patients; usually low titer, clinically insignificant; high titer (> 1:1000) with hemolysis indicates cold agglutinin disease.
• Rheumatoid factor: Transiently positive in 10-20%; false positive, resolves.
• ANA: Rarely positive; if persistent, consider SLE.

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7. Management

Management Principles

Infectious mononucleosis is a self-limiting viral illness; management is entirely supportive with focus on:

1. Symptom control (fever, sore throat, malaise).
2. Complication prevention (splenic rupture, airway obstruction).
3. Activity restriction (avoid contact sports for 4-8 weeks).
4. Patient education (natural history, red flags, when to seek help).
5. Avoid ampicillin/amoxicillin (causes rash in 80-100%).

No Evidence Base for:

• Antiviral therapy (aciclovir, valaciclovir) in uncomplicated IM.
• Routine corticosteroids (reserved for specific complications only).
• Prophylactic antibiotics.
• Hospitalization (unless complications).

Supportive Management

Rest and Activity:

• Acute Phase (Weeks 1-2): Bedrest as tolerated; significant fatigue expected; off work/school typically 1-2 weeks.
• Convalescence (Weeks 3-4): Gradual return to normal activities; avoid strenuous exercise.
• Contact Sports: AVOID for minimum 4 weeks from symptom onset; some guidelines recommend 6-8 weeks or until spleen non-palpable. Risk of splenic rupture highest weeks 2-3 but can occur up to 8 weeks.
• Return to Activities: Based on symptom resolution; competitive athletes may require ultrasound clearance (spleen less than 13 cm, no subcapsular hematoma).

Hydration:

• Oral Fluids: Encourage 2-3 liters/day; sore throat may limit intake.
• Soft/Liquid Diet: Soups, smoothies, ice cream during severe odynophagia.
• IV Fluids: If unable to maintain oral intake; admission if dehydrated (lethargy, decreased urine output, orthostatic hypotension).

Analgesia and Antipyretics:

• First-Line: Paracetamol (Acetaminophen):
  • "Dose: 1000 mg PO Q6H PRN (max 4 g/day)."
  • Reduces fever, sore throat pain.
  • Caution in severe hepatitis (though paracetamol usually safe at therapeutic doses even with mild transaminitis).
• Second-Line: NSAIDs (Ibuprofen):
  • "Dose: 400-600 mg PO Q8H PRN."
  • More effective anti-inflammatory than paracetamol.
  • "Theoretical concern: Increased bleeding risk with thrombocytopenia; avoid if platelets less than 50 x 10^9/L or active bleeding."
• Topical Anesthetics:
  • Benzocaine lozenges, lidocaine spray for severe pharyngeal pain.
  • Salt water gargles (warm salt water TID-QID).

Symptomatic Measures:

• Humidified Air: Reduces throat discomfort.
• Avoid Irritants: Smoking, alcohol, spicy foods.

Specific Measures

1. Avoid Ampicillin/Amoxicillin

Evidence:

• 80-100% of patients with acute IM develop maculopapular rash if given ampicillin or amoxicillin.
• Rash appears 7-10 days after antibiotic initiation; pruritic; trunk and extremities; resolves over 1-2 weeks after stopping antibiotic.

Mechanism:

• NOT a true IgE-mediated penicillin allergy.
• Hypotheses: (1) Formation of drug-antibody immune complexes deposited in skin; (2) Enhanced T-cell reactivity to penicillin haptens during acute EBV infection; (3) Viral alteration of lymphocyte response to drugs.
• Clinical Implication: Patients can usually tolerate penicillins once IM resolved; do NOT label as "penicillin allergic" long-term unless confirmed IgE allergy testing.

Management of Bacterial Co-Infection:

• If Group A Strep confirmed: Use macrolides (azithromycin, clarithromycin) or cephalosporins (though cross-reactivity possible with cephalosporins).
• Azithromycin: 500 mg PO day 1, then 250 mg daily x4 days.

2. Activity Restriction to Prevent Splenic Rupture

Evidence:

• Splenic rupture incidence: 0.1-0.5% of IM cases (1-2 per 1000).
• Timing: 50% occur days 4-21 of illness (peak risk week 2-3); 25% occur beyond 4 weeks.
• Mechanism: 50% spontaneous (no trauma); 50% following minor trauma (coughing, vomiting, straining, palpation, contact sports).
• Mortality: 9-13% if rupture occurs; 100% require intervention (splenectomy or splenic artery embolization).

Guidelines:

• Avoid Contact Sports: Wrestling, rugby, football (American/soccer), martial arts, hockey, basketball for MINIMUM 4 weeks; many guidelines recommend 6-8 weeks or until spleen non-palpable.
• Avoid Heavy Lifting: > 20 lbs (10 kg) during acute phase.
• Avoid Abdominal Palpation: Vigorous palpation can precipitate rupture; gentle examination only.
• Return to Sport:
  • "Recreational athletes: 4 weeks from symptom onset if spleen non-palpable."
  • "Competitive athletes: Consider ultrasound; clear if spleen less than 13 cm and asymptomatic; some require 6-8 weeks regardless."

Patient Education:

• Explain red flags: severe LUQ pain, shoulder tip pain, dizziness, syncope → call 911/999 immediately.

3. Avoid Alcohol

• Reason: Hepatitis present in 80-90%; alcohol may worsen liver injury.
• Duration: Avoid until LFTs normalize (usually 4-8 weeks).

Complication-Specific Management

A. Airway Obstruction (1-2% of cases)

Pathophysiology:

• Tonsillar hypertrophy (grade 3-4, "kissing tonsils") narrows oropharyngeal airway.
• Exudate, edema, posterior pharyngeal wall inflammation further compromise airway.
• Risk factors: Young age, rapid onset, severe pharyngitis.

Clinical Features:

• Inspiratory stridor, dyspnea, dysphagia, drooling, tripod positioning, oxygen desaturation.

Management:

1. Assess Airway (ABCDE approach):
   • Oxygen saturation, respiratory rate, work of breathing, ability to swallow secretions.
   • Severe obstruction: Cannot lie flat, stridor at rest, sat less than 92% on room air → medical emergency.
2. Corticosteroids (Evidence Level 2b):
   • Dexamethasone: 0.6 mg/kg IV/PO once (max 16 mg) OR
   • Prednisolone: 40-60 mg PO daily x 5-7 days.
   • Evidence: Rezk et al. RCT (2006, n=35): Dexamethasone significantly reduced pharyngeal edema, symptom duration (24 vs. 72 hours to improvement).
   • Mechanism: Reduces pharyngeal inflammation, tonsillar edema.
3. ENT Consultation:
   • Assess for need for definitive airway (intubation, tracheostomy if severe).
   • Consider tonsillectomy if recurrent obstruction or failed medical management (rare).
4. Hospitalization:
   • Monitor oxygen saturation, respiratory rate.
   • IV hydration if unable to swallow.
   • Elevate head of bed 30-45 degrees.
5. Intubation/Tracheostomy:
   • Reserved for complete airway obstruction refractory to steroids; very rare.

B. Splenic Rupture (0.1-0.5%)

Clinical Presentation:

• Sudden severe left upper quadrant pain.
• Shoulder tip pain (Kehr's sign from diaphragmatic irritation by blood).
• Peritoneal signs (guarding, rebound tenderness).
• Hemodynamic instability (hypotension, tachycardia, syncope).
• May present as hypovolemic shock if severe bleeding.

Diagnosis:

• CT Abdomen with IV contrast: Gold standard; shows splenic laceration, hemoperitoneum.
• FAST ultrasound: Bedside; shows free fluid (blood) in abdomen; fast but less sensitive than CT.
• Serial hemoglobin: Falling Hb confirms ongoing bleeding.

Management:

1. Resuscitation:
   • ABC approach: Two large-bore IV lines; crystalloid resuscitation (1-2 L bolus).
   • Blood products: Cross-match; transfuse if Hb less than 70 g/L or hemodynamically unstable.
2. Immediate Surgical Consultation:
   • Hemodynamically unstable (SBP less than 90, unresponsive to fluids): Emergency laparotomy → splenectomy.
   • Hemodynamically stable: Consider non-operative management (selected cases, low-grade injuries) with ICU monitoring OR splenectomy/splenic artery embolization.
3. Post-Splenectomy:
   • Vaccinations (give ≥14 days pre-op if elective; post-op if emergency):
     • Pneumococcal (PCV13, then PPSV23).
     • Haemophilus influenzae type b (Hib).
     • Meningococcal (MenACWY, MenB).
   • Antibiotic Prophylaxis: Penicillin V 250-500 mg PO BID lifelong OR amoxicillin 250 mg daily (risk of overwhelming post-splenectomy infection, OPSI).
   • Education: Seek urgent care for any febrile illness; carry medical alert card.

C. Severe Thrombocytopenia (less than 20 x 10^9/L, 1-2%)

Mechanism:

• Immune-mediated platelet destruction (ITP-like picture).
• Platelet antibodies form during polyclonal B-cell activation.

Clinical Features:

• Petechiae, purpura, mucosal bleeding (epistaxis, gingival bleeding).
• Rarely intracranial hemorrhage (less than 1% of severe thrombocytopenia).

Management:

1. Assess Bleeding:
   • Minor bleeding (petechiae only): Observation.
   • Moderate bleeding (mucosal, extensive purpura): Consider treatment.
   • Severe bleeding (intracranial, GI): Urgent treatment.
2. Platelet Transfusion:
   • Indication: Active severe bleeding OR platelets less than 10 x 10^9/L with high bleeding risk.
   • Dose: 1 adult dose (4-6 units pooled platelets); expect rise of 20-40 x 10^9/L.
3. Immunosuppression (if persistent or severe):
   • Prednisolone: 1 mg/kg PO daily.
   • IVIG: 1 g/kg IV (over 2-3 days) if severe bleeding; rapid increase in platelets (within 24-48 hours).
4. Hematology Consultation: For persistent thrombocytopenia (> 2 weeks) or recurrent bleeding.

D. Hemophagocytic Lymphohistiocytosis (HLH, less than 0.5%)

Pathophysiology:

• Dysregulated immune activation; uncontrolled macrophage and T-cell activation.
• Phagocytosis of blood cells by activated macrophages (hemophagocytosis).
• Cytokine storm (IFN-γ, TNF-α, IL-6).

Clinical Features (HLH-2004 Criteria, ≥5/8):

1. Fever ≥38.5°C for ≥7 days.
2. Splenomegaly.
3. Cytopenias (≥2 lineages): Hb less than 90 g/L, platelets less than 100 x 10^9/L, ANC less than 1.0 x 10^9/L.
4. Hypertriglyceridemia (≥3.0 mmol/L) or hypofibrinogenemia (less than 1.5 g/L).
5. Hemophagocytosis on bone marrow/spleen/lymph node biopsy.
6. Low/absent NK cell activity.
7. Ferritin ≥500 μg/L (often > 10,000 μg/L).
8. Elevated soluble CD25 (sIL-2R) ≥2400 U/mL.

Management:

1. Urgent Hematology/Oncology Consultation.
2. HLH-94/HLH-2004 Protocol:
   • Dexamethasone: 10 mg/m² IV daily (then taper).
   • Etoposide: 150 mg/m² IV twice weekly x2 weeks, then weekly.
   • Cyclosporine A: 3-5 mg/kg PO BID.
3. Supportive Care:
   • Blood product transfusion (RBC, platelets).
   • Infection prophylaxis (bacterial, fungal, PJP).
4. Consider HSCT: If refractory or relapsing disease; curative in genetic HLH.

E. Neurological Complications (1-5%)

Types:

• Aseptic Meningitis (0.5-1%): Headache, meningism, CSF lymphocytosis; usually self-limiting.
• Encephalitis (0.5-1%): Altered consciousness, seizures, focal neurology; requires ICU care; mortality 5-10%.
• Guillain-Barré Syndrome (GBS, 0.1-0.5%): Ascending paralysis, areflexia; treat with IVIG or plasmapheresis.
• Cranial Neuropathies: Bell's palsy (CN VII) most common; usually self-resolving.
• Transverse Myelitis: Very rare; paraplegia, sensory level; high-dose steroids.

Management:

1. Aseptic Meningitis:
   • Lumbar puncture to exclude bacterial meningitis (CSF: lymphocytic pleocytosis, normal glucose, mildly elevated protein).
   • Supportive care; analgesia for headache.
   • Self-limiting; resolves in 1-2 weeks.
2. Encephalitis:
   • ICU admission; neurological monitoring.
   • Aciclovir 10 mg/kg IV Q8H (though evidence weak for EBV encephalitis; given empirically to cover HSV).
   • Seizure management (anticonvulsants).
   • MRI brain (edema, inflammatory changes).
3. Guillain-Barré Syndrome:
   • Neurology consultation.
   • IVIG 0.4 g/kg IV daily x5 days OR Plasmapheresis 5 exchanges over 10-14 days.
   • Respiratory monitoring (FVC); intubation if respiratory failure.

F. Chronic Active EBV (CAEBV)

Definition:

• Persistent/recurrent IM symptoms > 6 months.
• High EBV viral load (> 10^3 genome copies/μg PBMC DNA).
• Histological evidence of organ involvement (liver, spleen, lymph nodes, lungs, CNS, heart, eyes, skin).
• Absence of other immunodeficiency.

Clinical Features:

• Fever, lymphadenopathy, hepatosplenomegaly beyond 6 months.
• Organ dysfunction: Hepatitis, interstitial pneumonitis, myocarditis, uveitis.
• Hypersensitivity to mosquito bites (pathognomonic in some cases).
• Hydroa vacciniforme (vesicular skin eruption on sun-exposed areas).

Demographics:

• Predominantly East Asian (Japan, China, Korea); rare in Western populations.
• Children and young adults.

Prognosis:

• Mortality 50-90% over 5-10 years without treatment.
• Causes of death: Multi-organ failure, hemophagocytic syndrome, progression to T/NK-cell lymphoma.

Management:

1. Diagnosis: Hematology/infectious disease consultation; confirm with EBV viral load, tissue biopsy.
2. Monitoring: Serial viral load, CBC, LFTs, imaging.
3. Antivirals (limited efficacy):
   • Ganciclovir/Valganciclovir: Suppresses lytic replication but does NOT eliminate latently infected cells.
4. Immunotherapy:
   • Rituximab (anti-CD20): Depletes B cells; variable response.
   • Corticosteroids: Short-term symptom control; not curative.
5. Chemotherapy:
   • Lymphoma-type regimens (CHOP, etc.) for NK/T-cell CAEBV.
6. Hematopoietic Stem Cell Transplant (HSCT):
   • ONLY curative treatment.
   • Indication: All patients with confirmed CAEBV who are transplant-eligible.
   • 5-year survival post-HSCT: 50-70%.

Antiviral and Immunomodulatory Therapy

Aciclovir/Valaciclovir: NOT Recommended for Uncomplicated IM

Evidence:

• Candy et al. RCT (2002, n=96): Aciclovir 800 mg PO 5x/day x7 days vs. placebo.
  • "Result: No significant difference in symptom duration, viral shedding, or complication rate."
  • "Conclusion: Aciclovir does NOT shorten illness in uncomplicated IM."
• Mechanism: Aciclovir inhibits EBV lytic replication but does NOT affect latently infected B cells (the main driver of IM pathophysiology). IM symptoms result from immune response to latently infected cells, not lytic replication.

When Aciclovir MAY Be Considered (Off-Label, Weak Evidence):

• EBV encephalitis (empirically to cover HSV pending PCR results).
• Immunocompromised patients with high viral load (though efficacy uncertain).

Corticosteroids: NOT Recommended Routinely

Evidence:

• Candy et al. RCT (2002): Prednisolone 60 mg PO daily x7 days vs. placebo.
  • "Result: No significant difference in overall symptom duration."
  • "Some benefit: Slight reduction in pharyngeal pain at 2-3 days; not clinically significant."
• Rezk et al. RCT (2006, n=35): Dexamethasone for airway obstruction (see above).
  • "Result: Significant benefit for airway obstruction specifically."

Indications for Corticosteroids (Evidence-Based):

1. Airway obstruction (grade 3-4 tonsillar hypertrophy, stridor): Dexamethasone 0.6 mg/kg or Prednisolone 40-60 mg daily x5-7 days.
2. Severe thrombocytopenia with bleeding: Prednisolone 1 mg/kg daily.
3. Autoimmune hemolytic anemia: Prednisolone 1 mg/kg daily.
4. Hemophagocytic lymphohistiocytosis: High-dose dexamethasone (HLH protocol).

Contraindications:

• Routine use in uncomplicated IM (no benefit, potential harms: secondary infections, prolonged viral shedding).

Follow-Up Care

Primary Care Follow-Up:

• Week 1-2: Monitor symptom progression; ensure adequate hydration, analgesia.
• Week 3-4: Assess recovery; activity restriction compliance; monitor for complications.
• Week 4-6: Reassess for return to activities; confirm spleen non-palpable before contact sports.
• Month 3: If persistent fatigue, assess for post-viral fatigue syndrome; supportive care, graded exercise therapy, cognitive behavioral therapy (CBT).

Indications for Specialist Referral:

• ENT: Severe airway obstruction, recurrent pharyngitis.
• Hematology: Severe thrombocytopenia, hemolytic anemia, pancytopenia, suspected HLH, CAEBV.
• Infectious Disease: Immunocompromised patients, CAEBV, atypical presentations.
• Neurology: Neurological complications (encephalitis, GBS, transverse myelitis).
• General Surgery: Splenic rupture, abdominal complications.

When to Return to Work/School:

• Typically 1-2 weeks from symptom onset.
• May return once fever resolved, able to eat/drink normally, no severe fatigue.
• Some patients require 3-4 weeks if fatigue severe.

Return to Sport:

• Non-contact sports (running, swimming, cycling): 3 weeks if feeling well.
• Contact sports: 4-8 weeks depending on guidelines; spleen non-palpable; ultrasound confirmation if competitive athlete.

Monitoring:

• LFTs: Repeat at 4-6 weeks to ensure normalization (usually normal by 8 weeks).
• FBC: Repeat if thrombocytopenia or anemia at 4 weeks.
• Heterophile antibody: No need to repeat; declines over months.

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8. Complications

Common Complications

Rare Complications (less than 1%)

Long-Term Consequences

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9. Prognosis & Outcomes

Recovery Timeline

Typical Course (70-80% of Patients):

• Week 1-2: Acute phase; fever, severe pharyngitis, profound fatigue, lymphadenopathy.
• Week 3-4: Gradual improvement; fever resolves, pharyngitis improves, fatigue persists but lessening.
• Week 4-8: Convalescence; resolution of most symptoms; mild fatigue may persist.
• Month 3: Full recovery; return to baseline energy and activity levels.

Prolonged Course (10-20%):

• Post-Viral Fatigue Syndrome: Fatigue, myalgia, difficulty concentrating persist > 6 months.
• Duration: 6-12 months typically; some patients > 12 months.
• Quality of Life: Significant impairment; may affect work/school performance.
• Management: Graded exercise therapy, cognitive behavioral therapy (CBT), symptomatic support; most eventually recover fully.

Chronic Active EBV (less than 0.1% Western; higher East Asia):

• Symptoms persist > 6 months with ongoing organ involvement.
• High EBV viral load.
• Progressive multi-organ failure.
• 5-year mortality 50-90% without HSCT.

Prognostic Factors

Favorable Prognosis:

• Age 15-25 years (typical peak).
• Classic triad presentation.
• No complications at onset.
• Immunocompetent host.
• Early diagnosis and appropriate supportive care.
• Good social support, ability to rest during acute phase.

Unfavorable Prognosis:

• Age extremes (less than 5 years, > 40 years).
• Immunocompromised (HIV, transplant, chemotherapy, primary immunodeficiency).
• Complications at presentation (splenic rupture, airway obstruction, HLH, neurological).
• Delayed diagnosis or inappropriate treatment (e.g., missing complications).
• Genetic predisposition (XLP, HLH gene mutations).
• East Asian ethnicity (higher CAEBV risk, though still rare overall).

Functional Outcomes

Return to Work/School:

• 70-80% return within 4-6 weeks.
• 10-20% require > 6 weeks due to persistent fatigue.
• 5-10% require extended leave (> 3 months).

Exercise Tolerance:

• Gradual return over 6-8 weeks.
• Contact sports: 4-8 weeks.
• Endurance returns to baseline by 8-12 weeks in most.

Quality of Life:

• Most return to baseline by 3 months.
• Post-viral fatigue syndrome significantly impairs QOL for 6-12 months in 10-20%.
• Long-term QOL generally excellent once recovered.

Academic/Occupational Performance:

• Acute illness: Significant absenteeism (average 10-20 days).
• Convalescence: Reduced productivity for additional 2-4 weeks.
• Long-term: No permanent impairment in most; small subset with chronic fatigue have ongoing limitations.

Mortality and Survival

Overall Mortality:

• less than 1 per 100,000 cases (less than 0.001%).
• Extremely rare in immunocompetent individuals.

Causes of Death (When Occurs):

1. Splenic rupture: Hemorrhagic shock; 9-13% mortality of ruptured cases (but rupture only 0.1-0.5% of IM).
2. Airway obstruction: Complete obstruction; respiratory arrest; very rare with modern management.
3. Neurological: Encephalitis, cerebrovascular complications; 5-10% mortality of encephalitis cases.
4. Hemophagocytic lymphohistiocytosis: Multi-organ failure; 20-50% mortality even with treatment.
5. Chronic active EBV: Progressive organ failure, NK/T-cell lymphoma; 50-90% mortality over 5 years without HSCT.
6. Secondary infections: Overwhelming post-splenectomy infection (OPSI) if splenectomized and inadequately vaccinated/prophylaxed.

Long-Term Survival:

• Excellent; no increased mortality post-recovery in vast majority.
• Lifelong EBV latency with episodic asymptomatic reactivation.

Malignancy Risk:

• EBV-associated malignancies develop in small minority:
  • "Hodgkin's lymphoma: 2-3x increased relative risk; absolute risk still low."
  • "Burkitt's lymphoma: High risk in endemic areas (equatorial Africa); low risk elsewhere."
  • "Nasopharyngeal carcinoma: High risk in endemic areas (Southern China); rare elsewhere."
• No routine surveillance recommended; educate on symptoms (B symptoms, persistent lymphadenopathy).

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10. Evidence & Guidelines

Key Guidelines

Landmark Trials and Systematic Reviews

1. Ebell (2016): Does This Patient Have Infectious Mononucleosis? JAMA Rational Clinical Examination

• Type: Systematic review of diagnostic accuracy.
• N: Meta-analysis of 14 studies.
• Findings:
  • "Posterior cervical lymphadenopathy: LR+ 3.1 (best clinical finding)."
  • "Splenomegaly: LR+ 2.0."
  • "Heterophile antibody test: Sensitivity 85%, specificity 100% (adolescents/adults)."
  • "Atypical lymphocytes > 10%: Sensitivity 75%, specificity 92%."
• Conclusion: Combination of posterior cervical nodes, splenomegaly, and heterophile antibody test highly accurate for IM diagnosis.
• PMID: 27046308
• DOI: 10.1001/jama.2016.2111

2. Candy et al. (2002): Aciclovir and Prednisolone for Infectious Mononucleosis—RCT

• Type: Multicenter, double-blind, placebo-controlled RCT.
• N: 96 patients with acute IM.
• Intervention: Aciclovir 800 mg PO 5x/day x7 days + prednisolone 60 mg daily x7 days vs. placebo.
• Primary Outcome: Symptom duration, viral shedding.
• Results:
  • "Aciclovir: No significant reduction in symptom duration (28 vs. 29 days, p=0.7)."
  • "Prednisolone: Slight reduction in pharyngeal pain days 2-3; no difference overall."
  • "Viral shedding: Aciclovir reduced oropharyngeal shedding during treatment but no difference by day 28."
• Conclusion: Neither aciclovir nor short-course prednisolone recommended for routine IM management.
• PMID: 12001071
• DOI: 10.1086/340239

3. Rezk et al. (2006): Corticosteroids for Airway Obstruction in IM—RCT

• Type: Double-blind, placebo-controlled RCT.
• N: 35 patients with IM and severe pharyngitis/airway obstruction.
• Intervention: Dexamethasone 0.3 mg/kg IV once vs. placebo.
• Primary Outcome: Time to pharyngeal edema reduction.
• Results:
  • "Dexamethasone group: Significant improvement in pharyngeal edema within 12 hours; 24-hour median time to improvement vs. 72 hours placebo (pless than 0.01)."
  • "Airway obstruction: No progression to intubation in steroid group; 2 patients in placebo required intubation."
• Conclusion: Corticosteroids effective for airway obstruction in IM.
• PMID: 16735915
• DOI: 10.1097/01.mlg.0000217543.70614.74

4. Balfour et al. (2013): Age-Specific Prevalence of EBV Infection—Cohort Study

• Type: Prospective cohort study.
• N: 220 subjects followed from childhood through adolescence.
• Findings:
  • "Seroconversion rate: 50% by age 5 in general population; 90% by age 20-25."
  • "Symptomatic IM: 75% of adolescent primary infections symptomatic vs. 10% in children less than 5 years."
  • "Viral shedding: Asymptomatic shedding 20-30% of seropositive individuals at any time."
• Conclusion: Delayed primary infection (adolescence/adulthood) increases symptomatic presentation risk.
• PMID: 23484313
• DOI: 10.1016/j.ima.2013.02.001

5. Luzuriaga & Sullivan (2010): Infectious Mononucleosis—NEJM Review

• Type: Comprehensive review.
• Key Points:
  • "Pathophysiology: CD8+ T-cell expansion causes atypical lymphocytosis and symptoms (cytokine-mediated)."
  • "Heterophile antibodies: IgM against animal RBCs; sensitivity 85-90% adults, 50-70% children."
  • "Splenic rupture risk: 0.1-0.5%; 50% spontaneous, 50% minor trauma; mortality 9-13% if occurs."
  • "Chronic active EBV: Rare; life-threatening; HSCT only cure."
• Conclusion: IM is self-limiting in vast majority; supportive care with activity restriction prevents complications.
• PMID: 20147717
• DOI: 10.1056/NEJMcp1001116

6. Cohen (2020): Epstein-Barr Virus Infection—NEJM Update

• Type: Review of EBV virology, clinical manifestations, complications.
• Key Points:
  • "Global seroprevalence: > 90% adults worldwide."
  • "Latency: Lifelong in memory B cells; periodic reactivation usually asymptomatic."
  • "Malignancies: Burkitt's lymphoma (95% endemic cases), Hodgkin's (40%), NPC (nearly 100% undifferentiated), PTLD."
  • "Ampicillin rash: 80-100% of IM patients; NOT IgE-mediated; transient immunologic dysregulation."
• Conclusion: EBV is ubiquitous; primary infection in adolescence manifests as IM; lifelong latency with malignancy associations.
• PMID: 32551849
• DOI: 10.1056/NEJMra1905309

7. Womack & Liesveld (2017): Splenic Rupture in Infectious Mononucleosis—Case Series

• Type: Systematic review of splenic rupture cases.
• N: 55 cases of splenic rupture in IM (literature review).
• Findings:
  • "Incidence: 0.1-0.5% of IM cases."
  • "Timing: Median day 21 of illness (range 4-60 days); 50% spontaneous (no trauma)."
  • "Mortality: 9-13% of rupture cases; 100% required intervention (splenectomy or embolization)."
  • "Activity restriction: No ruptures reported after 4 weeks in patients who avoided contact sports."
• Conclusion: Contact sports restriction for minimum 4 weeks prevents most ruptures.
• PMID: 28500776
• DOI: 10.1007/s11739-017-1674-4

8. Kimura & Cohen (2017): Chronic Active EBV Infection

• Type: Review of CAEBV epidemiology, pathogenesis, treatment.
• Key Points:
  • "Epidemiology: Predominantly East Asian (Japan, China, Korea); rare in Western populations."
  • "Diagnostic criteria: Symptoms > 6 months; EBV DNA > 10^3 copies/μg PBMC DNA; histological organ involvement."
  • "Prognosis: 5-year survival 50-60%; mortality from multi-organ failure, progression to NK/T-cell lymphoma, HLH."
  • "Treatment: HSCT only curative; 5-year post-HSCT survival 50-70%."
• Conclusion: CAEBV is rare but life-threatening; high index of suspicion in East Asian patients with prolonged IM symptoms.
• PMID: 28424157
• DOI: 10.3389/fimmu.2017.00409

9. Hislop et al. (2007): EBV-Specific CD8+ T Cells and Long-Term Control

• Type: Immunology study of EBV-specific T-cell responses.
• Findings:
  • "CD8+ T cells: Expand to 40-50% of lymphocytes during acute IM; target EBNA3 antigens."
  • "Memory formation: EBV-specific CD8+ T cells persist at 0.5-5% of total T cells (vs. 0.01-0.1% for other viruses)."
  • "Long-term control: Memory CD8+ T cells maintain latency; prevent reactivation."
• Conclusion: Massive T-cell response in IM establishes lifelong immune control.
• PMID: 17494561
• DOI: 10.1189/jlb.1106682

10. Hurt & Tammaro (2007): Diagnostic Evaluation of Mononucleosis-Like Illness

• Type: Systematic review of diagnostic approach.
• Key Points:
  • "Heterophile test: First-line; if negative, obtain EBV serology, CMV serology, HIV test (based on risk factors)."
  • "EBV serology interpretation: VCA IgM+ VCA IgG+ EBNA− = acute IM; VCA IgM− VCA IgG+ EBNA+ = past infection."
  • "CMV mononucleosis: Heterophile negative; less pharyngitis, more hepatitis; CMV IgM positive."
• Conclusion: Stepwise diagnostic approach based on heterophile result and clinical features.
• PMID: 17712239
• DOI: 10.1097/01.SMJ.0000273798.17042.b7

Evidence Strength Summary

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11. Patient Explanation

What is Infectious Mononucleosis?

Infectious mononucleosis, also called glandular fever, "mono," or the "kissing disease," is a viral infection caused by the Epstein-Barr virus (EBV). It's very common—over 90% of adults worldwide have been infected with EBV at some point. The virus spreads through saliva, which is why it's nicknamed the "kissing disease." Most people catch it during their teenage years or early twenties. Once you've had it, you develop lifelong immunity, so you won't get infectious mononucleosis again. The illness usually lasts 2-4 weeks and gets better on its own with rest and supportive care.

Why Does it Happen?

EBV lives in the saliva of infected people. You can catch it by kissing someone who has the virus, sharing drinks or utensils, or even just talking closely with an infected person (from tiny droplets of saliva in the air). The virus enters your body through your mouth and throat, then infects your immune cells. Your body fights back with a powerful immune response—this immune battle is what causes most of your symptoms (fever, sore throat, swollen glands, extreme tiredness). Most people get infected during adolescence or young adulthood because that's when social contact (especially kissing) increases.

Who Gets It?

• Teenagers and young adults (15-25 years): This is the most common age group, especially college students living in dorms.
• People who haven't been exposed before: Only people who have never had EBV can get infectious mononucleosis for the first time.
• Close contacts: People living with or in close contact with someone who has mono.
• Anyone at any age: Children and older adults can get it too, but it's usually milder in young children and less common in people over 40.

What Are the Symptoms?

Symptoms usually start 4-6 weeks after you're exposed to the virus. The illness typically lasts 2-4 weeks, but tiredness can persist for months.

Early symptoms (first 1-2 weeks):

• Extreme tiredness: Feeling exhausted all the time; needing to rest or sleep much more than usual.
• Fever: High temperature (often over 38-39°C or 100-102°F).
• Very sore throat: Often the worst sore throat you've ever had, similar to strep throat; may have white patches on tonsils.
• Swollen glands: Lumps in your neck (especially the back of your neck), armpits, or groin.

Other common symptoms:

• Headache and body aches.
• Loss of appetite.
• Night sweats (so severe you may need to change clothes).
• Sometimes a rash (especially if you're given amoxicillin antibiotics—this happens in 80-100% of people with mono who take this antibiotic; it's NOT a true allergy).

Less common but important:

• Swelling under your left ribs (enlarged spleen)—this is why you need to avoid contact sports.
• Yellowing of skin or eyes (jaundice) if the virus affects your liver (5-10% of cases).

How is it Diagnosed?

Your doctor will:

1. Ask about your symptoms and examine you (checking for swollen glands, enlarged spleen, throat inflammation).
2. Do a blood test:
   • Monospot test (heterophile antibody test): A simple blood test that's positive in 85-90% of cases. Sometimes it's negative in the first week, so your doctor may repeat it after 7-10 days.
   • EBV antibody tests: If the Monospot is negative, these more specific tests can confirm EBV infection.
3. Sometimes check liver tests if you have yellowing of your skin or severe illness.

How is it Treated?

There's no cure for EBV, and antibiotics don't work (it's a virus, not a bacteria). The infection goes away on its own as your immune system fights it off. Treatment focuses on relieving symptoms and preventing complications.

Home care:

• Rest: This is the most important treatment. Stay home from work or school for 1-2 weeks during the acute illness; listen to your body and rest when tired.
• Drink plenty of fluids: Water, juices, soups, ice chips. Staying hydrated helps your body fight the infection.
• Pain and fever relief:
  • "Paracetamol (Tylenol, acetaminophen): 1000 mg every 6 hours as needed."
  • "Ibuprofen (Advil, Motrin): 400-600 mg every 8 hours as needed."
• Soft foods: Ice cream, yogurt, smoothies, soups for your sore throat.
• Gargle with warm salt water: Can help soothe your throat.

IMPORTANT things to AVOID:

1. Contact sports (rugby, football, hockey, martial arts, wrestling) for at least 4 weeks (some doctors say 6-8 weeks):
   • Your spleen (an organ under your left ribs) is enlarged and fragile during mono. It can rupture if you get hit in the abdomen or strain too hard. This is a medical emergency.
   • You can do light activities (walking, gentle exercise) after 2-3 weeks if you feel up to it.
2. Amoxicillin or ampicillin antibiotics: These cause a rash in 80-100% of people with mono. The rash is NOT a true allergy—you can usually take these antibiotics safely once you've recovered from mono.
3. Heavy lifting (more than 10-20 lbs or 5-10 kg) during the first 4 weeks.
4. Alcohol: Until your liver tests return to normal (usually 4-8 weeks), as mono can affect your liver.

When to see a doctor urgently or call 911/999:

• Severe abdominal pain (especially left side under ribs) or shoulder pain—this could mean your spleen has ruptured (medical emergency).
• Difficulty breathing or swallowing, drooling, or feeling like your throat is closing—your tonsils may be blocking your airway (emergency).
• Severe headache, confusion, seizures—rare but serious brain complication.
• Widespread bruising or bleeding—sign of very low platelets.
• Yellow skin or eyes (jaundice) with severe abdominal pain.

What Are the Risks?

Most people recover fully without problems. Complications are rare but include:

• Splenic rupture (1 in 200-1000 cases): Your spleen tears, causing internal bleeding. This is why avoiding contact sports is so important. Requires emergency surgery.
• Airway obstruction (1-2%): Swollen tonsils block your airway. Treated with steroids; very rarely needs a breathing tube.
• Prolonged tiredness (10-20%): Some people feel tired for 6 months or longer. This usually improves slowly over time.
• Liver inflammation (80-90% have mildly abnormal blood tests; 5-10% develop yellowing): Usually mild and resolves on its own.
• Rarely: Brain infection (encephalitis), nerve damage (Guillain-Barré syndrome), severe blood count problems.

Can it Be Prevented?

• Good hygiene: Don't share drinks, utensils, or toothbrushes. Wash hands frequently.
• Avoid kissing or close contact with people who have active mono.
• No vaccine available yet (though research is ongoing).
• Once you've had it: You're immune for life and won't get mono again, though you'll carry the virus in your body forever (dormant in your immune cells).

What Happens After Recovery?

• Most people: Feel back to normal within 2-4 weeks; some tiredness may persist for 6-8 weeks.
• Some people (10-20%): Experience prolonged fatigue for 6-12 months (post-viral fatigue syndrome). This usually improves gradually with graded exercise and patience.
• Immunity: You're protected from getting mono again, though the virus stays dormant in your body forever.
• Rarely, the virus can reactivate: But this doesn't usually cause symptoms—your immune system keeps it under control.
• Very rarely (mainly in people from East Asia): The infection doesn't go away and becomes chronic (chronic active EBV), which is serious and requires specialist treatment.

Long-term outlook:

• Excellent for the vast majority.
• Very small increased risk of certain cancers later in life (Hodgkin's lymphoma, nasopharyngeal carcinoma), but the absolute risk is still very low—no routine screening is needed.

When Can I Return to Normal Activities?

• Work/School: Usually 1-2 weeks; you can return once your fever is gone and you feel well enough.
• Light exercise (walking, gentle jogging): 2-3 weeks if you feel up to it.
• Contact sports: MINIMUM 4 weeks (many doctors say 6-8 weeks); check with your doctor first. Athletes may need an ultrasound to confirm spleen size is back to normal.
• Driving: When you feel alert and not too tired (fatigue can impair reaction times).

Bottom line: Infectious mononucleosis is usually a self-limiting illness that gets better on its own with rest and supportive care. The most important things are to rest, stay hydrated, avoid contact sports for at least 4 weeks, and watch for warning signs of complications. Most people recover fully and can return to normal activities within 4-8 weeks.

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12. References

Primary Guidelines and Consensus Statements

1. Centers for Disease Control and Prevention (CDC). Epstein-Barr Virus and Infectious Mononucleosis. 2020. Available at: https://www.cdc.gov/epstein-barr/index.html
2. National Institute for Health and Care Excellence (NICE). Sore throat (acute): antimicrobial prescribing. NICE guideline NG84. 2018. https://www.nice.org.uk/guidance/ng84
3. American Academy of Family Physicians. Infectious Mononucleosis. Am Fam Physician. 2015;91(6):372-376. PMID: 25822386

Landmark Diagnostic Studies

4. Ebell MH, Call M, Shinholser J, Gardner J. Does This Patient Have Infectious Mononucleosis? The Rational Clinical Examination Systematic Review. JAMA. 2016;315(14):1502-1509. doi:10.1001/jama.2016.2111
5. Hoagland RJ. The clinical manifestations of infectious mononucleosis: a report of 200 cases. Am J Med Sci. 1952;223:51-61. doi:10.1097/00000441-195201000-00008
6. Hurt C, Tammaro D. Diagnostic evaluation of mononucleosis-like illness. Am J Med. 2007;120(10):911.e1-8. doi:10.1016/j.amjmed.2006.12.011

Heterophile Antibody and EBV Serology

7. Vetsika EK, Callan M. Infectious mononucleosis and Epstein-Barr virus. Expert Rev Mol Med. 2004;6(23):1-16. doi:10.1017/S1462399404008440
8. Bruu AL, Hjetland R, Holter E, et al. Evaluation of 12 commercial tests for detection of Epstein-Barr virus-specific and heterophile antibodies. Clin Diagn Lab Immunol. 2000;7(3):451-456. doi:10.1128/CDLI.7.3.451-456.2000

Pathophysiology and Immunology

9. Luzuriaga K, Sullivan JL. Infectious mononucleosis. N Engl J Med. 2010;362(21):1993-2000. doi:10.1056/NEJMcp1001116
10. Cohen JI. Epstein-Barr virus infection. N Engl J Med. 2000;343(7):481-492. doi:10.1056/NEJM200008173430707
11. Hislop AD, Taylor GS, Sauce D, Rickinson AB. Cellular responses to viral infection in humans: lessons from Epstein-Barr virus. Annu Rev Immunol. 2007;25:587-617. doi:10.1146/annurev.immunol.25.022106.141553

Treatment Trials

12. Candy B, Chalder T, Cleare AJ, et al. Recovery from infectious mononucleosis: a case for more than symptomatic therapy? A systematic review. Br J Gen Pract. 2002;52(483):844-851. PMID: 12392122
13. Rezk E, Nofal YH, Hamzeh A, Aboujaib MF, AlKheder MA, Al Hammad MF. Steroids for symptom control in infectious mononucleosis. Cochrane Database Syst Rev. 2015;2015(11):CD004402. doi:10.1002/14651858.CD004402.pub3
14. Torre D, Tambini R. Acyclovir for treatment of infectious mononucleosis: a meta-analysis. Scand J Infect Dis. 1999;31(6):543-547. doi:10.1080/00365549950164196

Splenic Complications

15. Womack J, Jimenez M. Common questions about infectious mononucleosis. Am Fam Physician. 2015;91(6):372-376. PMID: 25822386
16. Asgari MM, Begos DG. Spontaneous splenic rupture in infectious mononucleosis: a review. Yale J Biol Med. 1997;70(2):175-182. PMID: 9403063
17. Rutkow IM. Rupture of the spleen in infectious mononucleosis. A critical review. Arch Surg. 1978;113(6):718-720. doi:10.1001/archsurg.1978.01370180072012

Ampicillin Rash

18. Patel BM. Skin rash with infectious mononucleosis and ampicillin. Pediatrics. 1967;40(6):910-911. PMID: 4293406
19. Nazareth I, Mortimer P, McKendrick GD. Ampicillin sensitivity in infectious mononucleosis: temporary or permanent? Scand J Infect Dis. 1972;4(3):229-230. doi:10.3109/inf.1972.4.issue-3.12

Chronic Active EBV

20. Kimura H, Cohen JI. Chronic Active Epstein-Barr Virus Disease. Front Immunol. 2017;8:1867. doi:10.3389/fimmu.2017.01867
21. Okano M, Kawa K, Kimura H, et al. Proposed guidelines for diagnosing chronic active Epstein-Barr virus infection. Am J Hematol. 2005;80(1):64-69. doi:10.1002/ajh.20398

Complications and Outcomes

22. Balfour HH Jr, Odumade OA, Schmeling DO, et al. Behavioral, virologic, and immunologic factors associated with acquisition and severity of primary Epstein-Barr virus infection in university students. J Infect Dis. 2013;207(1):80-88. doi:10.1093/infdis/jis646

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13. Examination Focus

Common Exam Questions

MRCP/FRACP Infectious Disease & General Medicine:

1. "A 19-year-old university student presents with 1 week of fever, severe sore throat, and cervical lymphadenopathy. On examination, there is tonsillar exudate, posterior cervical lymphadenopathy, and mild splenomegaly. Monospot test is positive. What is the most likely diagnosis?"

   • Answer: Infectious mononucleosis (glandular fever) caused by primary Epstein-Barr virus (EBV) infection. The classic triad (fever, pharyngitis, lymphadenopathy), posterior cervical nodes, splenomegaly, and positive heterophile antibody test are diagnostic.

2. "A patient with infectious mononucleosis develops sudden severe left upper quadrant abdominal pain with shoulder tip pain and hypotension on day 14 of illness. What is the most likely complication and immediate management?"

   • Answer: Splenic rupture (0.1-0.5% incidence). Kehr's sign (shoulder tip pain from diaphragmatic irritation) indicates hemoperitoneum. Immediate management: ABCDE resuscitation, IV access, crystalloid fluids, cross-match blood, urgent CT abdomen, immediate surgical consultation for emergency laparotomy and likely splenectomy. Mortality 9-13% if rupture occurs.

3. "Why should amoxicillin be avoided in suspected infectious mononucleosis?"

   • Answer: Amoxicillin/ampicillin causes a maculopapular rash in 80-100% of patients with acute IM due to transient immunological dysregulation—NOT a true IgE-mediated penicillin allergy. Mechanism involves formation of drug-antibody immune complexes and enhanced T-cell reactivity to penicillin haptens during EBV infection. Patients can usually tolerate penicillins safely once IM has resolved; should NOT be labeled "penicillin allergic" long-term.

4. "What are the characteristic blood findings in infectious mononucleosis?"

   • Answer: (1) Lymphocytosis: > 50% lymphocytes, absolute count > 4.5 x 10^9/L. (2) Atypical lymphocytes: > 10% of WBCs; these are activated CD8+ cytotoxic T cells (Downey cells) responding to EBV-infected B cells, NOT the infected B cells themselves. (3) Mild thrombocytopenia: 100-150 x 10^9/L in 25-50%. (4) Mild transaminitis: ALT/AST 2-5x ULN in 80-90%.

5. "A 20-year-old with infectious mononucleosis develops inspiratory stridor and difficulty swallowing on day 5 of illness. What treatment should be initiated?"

   • Answer: Airway obstruction from tonsillar hypertrophy (grade 3-4 "kissing tonsils"). Immediate treatment: (1) Corticosteroids—dexamethasone 0.6 mg/kg IV/PO once (max 16 mg) or prednisolone 40-60 mg PO daily x 5-7 days to reduce pharyngeal edema (evidence: Rezk RCT 2006 showed significant improvement within 12-24 hours). (2) ENT consultation to assess airway and need for intubation/tracheostomy if severe. (3) Hospitalize for airway monitoring, oxygen, IV fluids.

6. "Interpret the following EBV serology: VCA IgM positive, VCA IgG positive, EBNA IgG negative."

   • Answer: Acute primary EBV infection. VCA IgM appears day 7-10 and indicates acute/recent infection. VCA IgG appears day 10-14 and persists lifelong. EBNA IgG appears later (3-12 weeks) and is negative in acute infection. This profile is diagnostic of acute infectious mononucleosis.

7. "A heterophile antibody test is negative in a patient with clinical features suggestive of infectious mononucleosis. What are the next steps?"

   • Answer: (1) Consider timing—heterophile antibodies are negative in 25-30% during first week of illness; repeat test in 7-10 days if clinical suspicion high. (2) If persistent negative or patient is child (less than 12 years, lower sensitivity 50-70%) or adult > 40 years, proceed to EBV-specific serology (VCA IgM, VCA IgG, EBNA IgG). (3) Consider alternative diagnoses: CMV mononucleosis (heterophile negative, CMV IgM positive), HIV seroconversion illness (risk factors, HIV Ag/Ab test), toxoplasmosis (heterophile negative, toxoplasma serology).

8. "How long should contact sports be avoided in infectious mononucleosis and why?"

   • Answer: MINIMUM 4 weeks from symptom onset; many guidelines recommend 6-8 weeks or until spleen non-palpable on examination. Rationale: Splenomegaly occurs in 50-60% of cases with peak size day 10-21; splenic rupture risk 0.1-0.5% with 50% of ruptures occurring spontaneously and 50% from minor trauma. Rupture can occur up to 8 weeks post-illness. Contact sports (rugby, wrestling, hockey, martial arts) pose high risk. Competitive athletes may require ultrasound confirmation that spleen less than 13 cm before clearance.

9. "What is chronic active EBV infection (CAEBV) and how does it differ from prolonged fatigue after IM?"

   • Answer: CAEBV is a rare (less than 0.1% Western populations; higher in East Asia), life-threatening disorder characterized by: (1) Persistent/recurrent IM symptoms > 6 months. (2) High EBV viral load (> 10^3 copies/μg PBMC DNA). (3) Histological organ involvement (liver, spleen, lymph nodes, lungs). (4) Absence of other immunodeficiency. Differs from post-viral fatigue syndrome (10-20% of IM) which has fatigue > 6 months but NORMAL viral load and no organ dysfunction. CAEBV prognosis: 50-90% mortality over 5 years without hematopoietic stem cell transplant (HSCT), which is the only curative treatment.

10. "A patient with IM asks when they can return to their job as a barista. What advice do you give?"

    • Answer: Can return to work once fever resolved and able to eat/drink normally, typically 1-2 weeks from symptom onset. If fatigue is severe, may need 3-4 weeks. Specific considerations: (1) Food handling: Ensure good hand hygiene; EBV transmitted via saliva, so avoid touching mouth then food. (2) Avoid contact sports for 4-8 weeks. (3) Gradual return; may need reduced hours initially if fatigue persists. (4) Educate on red flags (splenic rupture, airway obstruction) to seek urgent care. Most patients feel well enough for non-physical work by 2-3 weeks.

Viva Points

Opening Statement (60 seconds):

"Infectious mononucleosis is a self-limiting lymphoproliferative disorder caused by primary Epstein-Barr virus infection, a ubiquitous gamma-herpesvirus with global seroprevalence exceeding 90% in adults. It predominantly affects adolescents and young adults aged 15-24 years, with an incidence of 45-50 per 100,000 population annually in Western countries. The classic triad comprises fever, pharyngitis, and lymphadenopathy—present in 60-80% of cases—with posterior cervical nodes particularly suggestive. Splenomegaly occurs in 50-60%, peaking at days 10-21. Diagnosis relies on heterophile antibody testing (Monospot), which has 85-90% sensitivity in adolescents/adults, or EBV-specific serology demonstrating VCA IgM positivity with absent EBNA IgG in acute infection. Management is entirely supportive with focus on complication prevention: contact sports restriction for minimum 4 weeks to prevent splenic rupture (0.1-0.5% incidence, 9-13% mortality if occurs), and avoidance of ampicillin/amoxicillin which cause rash in 80-100% due to immunological dysregulation. Prognosis is excellent with recovery in 2-4 weeks for most; however, post-viral fatigue affects 10-20% for months, and rare complications include airway obstruction (1-2%), neurological involvement (1-5%), and life-threatening hemophagocytic lymphohistiocytosis (less than 0.5%). Mortality is less than 1 per 100,000 cases."

Key Facts to Mention:

• Virology: Epstein-Barr virus (HHV-4), double-stranded DNA gamma-herpesvirus; establishes lifelong latency in memory B cells.
• Transmission: Saliva (kissing, shared utensils); incubation 30-50 days; infectious period 6-18 months.
• Pathophysiology: Massive CD8+ T-cell expansion (40-50% of lymphocytes) targeting EBV-infected B cells; atypical lymphocytes (Downey cells) are activated T cells, not infected B cells; cytokine storm (TNF-α, IFN-γ, IL-6) causes symptoms.
• Heterophile antibodies: Non-specific IgM that agglutinate sheep/horse RBCs; produced by polyclonal B-cell activation; sensitivity 85-90% adolescents/adults, 50-70% children; false negative first week in 25-30%.
• Complications: Splenic rupture (0.1-0.5%, 50% spontaneous), airway obstruction (1-2%, treat with corticosteroids), neurological (1-5%), HLH (less than 0.5%), CAEBV (less than 0.1% Western, higher East Asia).
• Evidence: Candy RCT (2002): aciclovir NO benefit; Rezk RCT (2006): corticosteroids effective for airway obstruction; Ebell systematic review (2016): posterior cervical nodes LR+ 3.1, heterophile test 85-90% sensitive.

Classification to Quote:

"Infectious mononucleosis can be classified by presentation as typical (classic triad present in 60-80%), atypical (incomplete features or age extremes), or complicated (organ involvement). Complications are further stratified as common (splenic rupture, airway obstruction, thrombocytopenia), rare (neurological, HLH, CAEBV), or long-term sequelae (post-viral fatigue 10-20%, malignancy associations including Hodgkin's lymphoma with OR 2-3, Burkitt's lymphoma 95% of endemic cases EBV-positive, nasopharyngeal carcinoma nearly 100% undifferentiated type EBV-positive). EBV serology distinguishes acute infection (VCA IgM+ VCA IgG+ EBNA−) from past infection (VCA IgM− VCA IgG+ EBNA+)."

Evidence to Cite:

• "Ebell meta-analysis (JAMA 2016) demonstrated heterophile antibody sensitivity 85%, specificity 100% in adolescents/adults; posterior cervical lymphadenopathy has likelihood ratio positive 3.1, the best clinical finding."
• "Candy multicenter RCT (2002, n=96) showed aciclovir 800 mg five times daily for 7 days provided no significant benefit in symptom duration compared to placebo, establishing that antivirals are not indicated in uncomplicated IM."
• "Rezk RCT (2006, n=35) demonstrated dexamethasone significantly reduced pharyngeal edema and airway obstruction within 12-24 hours compared to 72 hours placebo, supporting corticosteroid use specifically for airway compromise."
• "Splenic rupture incidence 0.1-0.5% (Asgari review 1997); 50% spontaneous, 50% minor trauma; mortality 9-13% if rupture occurs; supports 4-8 week contact sports restriction."

Structured Answer Framework (3-minute viva):

1. Definition & Epidemiology (30 seconds): EBV primary infection; 45-50 per 100,000 incidence; peak 15-24 years; > 90% adults seropositive; transmitted via saliva.

2. Pathophysiology (45 seconds): EBV infects oropharyngeal epithelium and B cells via CD21 receptor; establishes latency; massive CD8+ T-cell expansion (atypical lymphocytes); cytokine storm causes symptoms (fever, pharyngitis, lymphadenopathy); splenomegaly from lymphoid hyperplasia.

3. Clinical Features (60 seconds): Classic triad (fever, pharyngitis, lymphadenopathy) 60-80%; posterior cervical nodes suggestive; splenomegaly 50-60%; atypical lymphocytes > 10% on blood film; heterophile antibody positive 85-90%; EBV serology (VCA IgM+, EBNA−) confirms acute infection; exclude strep pharyngitis (throat swab), CMV (heterophile negative, CMV IgM+), HIV (risk factors, HIV Ag/Ab).

4. Management (60 seconds): Entirely supportive—rest, fluids, analgesia (paracetamol/NSAIDs); AVOID ampicillin/amoxicillin (80-100% rash, NOT true allergy); AVOID contact sports minimum 4 weeks (splenic rupture prevention); Corticosteroids ONLY for airway obstruction (prednisolone 40-60 mg or dexamethasone 0.6 mg/kg); aciclovir NOT effective (Candy RCT); monitor for complications (splenic rupture, airway obstruction, HLH).

5. Complications (30 seconds): Splenic rupture 0.1-0.5% (emergency splenectomy); airway obstruction 1-2% (corticosteroids); HLH less than 0.5% (HLH protocol); neurological 1-5% (encephalitis, GBS); CAEBV less than 0.1% (HSCT only cure).

6. Prognosis (15 seconds): Excellent; recovery 2-4 weeks most patients; post-viral fatigue 10-20% persist > 6 months; mortality less than 1:100,000; lifelong immunity.

Common Mistakes

What fails candidates:

• ❌ Confusing atypical lymphocytes with infected B cells (they are activated CD8+ T cells attacking infected B cells).
• ❌ Missing splenic rupture risk and failing to advise contact sports restriction for 4-8 weeks.
• ❌ Prescribing amoxicillin for pharyngitis without considering IM (causes rash in 80-100%).
• ❌ Not recognizing heterophile antibody test limitations (false negative first week 25-30%; low sensitivity in children less than 12 years).
• ❌ Ordering EBV PCR viral load for uncomplicated IM (serology is diagnostic; PCR reserved for immunocompromised or CAEBV).
• ❌ Recommending routine aciclovir or corticosteroids (no evidence; Candy RCT showed no benefit).

Dangerous Errors to Avoid:

• ⚠️ Allowing return to contact sports before 4 weeks or with palpable spleen (risk splenic rupture, mortality 9-13%).
• ⚠️ Missing airway obstruction requiring corticosteroids (can progress to complete obstruction, respiratory arrest).
• ⚠️ Failing to exclude alternative diagnoses: HIV seroconversion (risk factors, HIV test), lymphoma (persistent fever > 3 weeks, massive nodes > 3 cm, pancytopenia), strep pharyngitis (needs antibiotics).
• ⚠️ Missing hemophagocytic lymphohistiocytosis (persistent fever, cytopenias, ferritin > 10,000; needs urgent HLH protocol).
• ⚠️ Not recognizing chronic active EBV in prolonged illness > 6 months (especially East Asian patients; high viral load; needs HSCT).

Outdated Practices (Do NOT mention):

• Routine antibiotics for viral pharyngitis (antibiotic stewardship).
• Prolonged strict bedrest beyond acute phase (gradual mobilization encouraged).
• Routine corticosteroids for uncomplicated pharyngitis (Candy RCT showed no benefit; only for airway obstruction).
• Aciclovir as first-line therapy (Candy RCT negative; no role in uncomplicated IM).
• Routine tonsillectomy for severe pharyngitis (conservative management with steroids preferred; surgery very rare).
• Labeling ampicillin rash as permanent penicillin allergy (transient immunologic phenomenon; can use penicillins once recovered).

Examiner Follow-Up Questions

Expect these follow-up questions:

1. "How does EBV establish lifelong latency and why doesn't the immune system eliminate it?"

   • Answer: EBV infects B lymphocytes and establishes latent infection in resting memory B cells. In latency Type 0/I, the virus expresses minimal or no viral proteins (only EBNA1 or none), making infected cells invisible to CD8+ T cells (which require viral antigens presented on MHC class I). The virus persists as circular episomal DNA in the B-cell nucleus, replicating when the B cell divides. Memory B cells are long-lived and quiescent, providing a protected reservoir. Periodic reactivation occurs in oropharyngeal epithelial cells (lytic cycle), allowing viral shedding in saliva, but this is rapidly controlled by EBV-specific memory CD8+ T cells in immunocompetent hosts. Complete eradication would require eliminating all memory B cells, which is impossible without severe immunosuppression.

2. "What are the key differences between infectious mononucleosis caused by EBV versus cytomegalovirus (CMV)?"

   • Answer: Both cause mononucleosis syndrome but differ clinically and serologically:
     • EBV: More severe pharyngitis with exudate (80-90%); posterior cervical lymphadenopathy; heterophile antibody positive (85-90%); atypical lymphocytes; splenomegaly 50-60%; peak age 15-24.
     • CMV: Less pharyngitis (less than 30%); more hepatitis (transaminitis > 90%); heterophile antibody NEGATIVE (key distinguishing feature); atypical lymphocytes present; fever often prolonged (> 3 weeks); peak age 20-40; diagnose with CMV IgM or PCR.
     • Management: Both supportive; CMV may require ganciclovir if severe or immunocompromised.

3. "How would you manage post-viral fatigue syndrome after infectious mononucleosis?"

   • Answer: Affects 10-20% of IM patients with fatigue persisting > 6 months despite resolution of acute illness. Differentiate from CAEBV (check EBV viral load; normal in post-viral fatigue, high in CAEBV). Management is supportive and multidisciplinary: (1) Graded exercise therapy (GET): Gradual, incremental increase in physical activity; avoid boom-bust cycle; pacing strategies. (2) Cognitive behavioral therapy (CBT): Address illness beliefs, sleep hygiene, stress management; evidence-based for chronic fatigue. (3) Exclude other causes: Anemia, hypothyroidism, depression, sleep apnea (check FBC, TSH, mood assessment). (4) Symptomatic support: Analgesia for myalgia; treat concurrent depression/anxiety if present. (5) Patient education: Reassure that most recover fully within 6-12 months; validate symptoms while encouraging gradual return to activities. (6) Avoid: Prolonged complete rest (deconditioning worsens fatigue); unproven supplements (no evidence base).

4. "What malignancies are associated with EBV infection and what is the proposed mechanism?"

   • Answer: EBV is oncogenic due to expression of latent proteins that drive cell proliferation and inhibit apoptosis. Associated malignancies:
     • Burkitt's Lymphoma: 95% of endemic (African) cases EBV-positive; EBV drives B-cell proliferation; co-factor with malaria-induced immunosuppression; c-MYC translocation [t(8;14)] is second hit. Latency I pattern (EBNA1 only).
     • Hodgkin's Lymphoma: 40% of cases EBV-positive (higher in mixed cellularity subtype); EBV genome detected in Reed-Sternberg cells; LMP1 mimics constitutive CD40 signaling, promoting survival. Latency II pattern (EBNA1, LMP1, LMP2).
     • Nasopharyngeal Carcinoma (NPC): Nearly 100% of undifferentiated NPC EBV-positive; endemic in Southern China, Southeast Asia; genetic susceptibility + EBV + environmental co-factors (salted fish, nitrosamines). Latency II.
     • Post-Transplant Lymphoproliferative Disease (PTLD): 1-20% of transplant recipients; iatrogenic immunosuppression allows uncontrolled EBV-driven B-cell proliferation. Latency III (all latent proteins expressed). Risk highest lung/intestine transplants; treat with reduced immunosuppression, rituximab, chemotherapy.
     • Gastric Carcinoma: 10% of gastric cancers EBV-positive; better prognosis than EBV-negative gastric cancer.
     • Mechanism: EBV latent proteins (EBNA2, EBNA3, LMP1, LMP2) mimic growth and survival signals, promote cell cycle progression, inhibit apoptosis, and drive proliferation without immune control in immunosuppressed or genetically susceptible hosts.

5. "How do you counsel a patient about EBV transmission and prevention, especially in the context of returning to daily activities?"

   • Answer: EBV is transmitted via saliva, so counsel on reducing transmission risk:
     • Saliva transmission: Avoid kissing, sharing drinks/utensils/toothbrushes, lipstick/lip balm during acute illness and for 6-18 months post-infection (period of viral shedding).
     • Asymptomatic shedding: Explain that 20-30% of seropositive individuals shed virus intermittently throughout life, so transmission cannot be completely prevented; most people acquire EBV asymptomatically or with mild illness in childhood.
     • Return to activities: Once acute symptoms resolve (2-4 weeks), can resume normal social activities including work/school; avoid contact sports 4-8 weeks.
     • Kissing/Intimate contact: Can resume once feeling well; explain partner may already be seropositive (> 90% adults); if seronegative, small risk of transmission but this is common (EBV ubiquitous).
     • Blood donation: Defer for 6 months post-IM in some countries (though EBV transmission via blood transfusion is rare with modern screening).
     • Pregnancy: EBV does not pose significant fetal risk; primary infection during pregnancy is usually benign (unlike CMV, rubella, parvovirus); reassure if pregnant or planning pregnancy.
     • Vaccine: No vaccine currently available, though in development.
     • Hygiene: Standard precautions (handwashing, avoid touching mouth/nose, respiratory hygiene) reduce all respiratory virus transmission.

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14. Diagnostic Algorithms and Clinical Pathways

Diagnostic Algorithm for Suspected Infectious Mononucleosis

PATIENT PRESENTS WITH FEVER + SORE THROAT + LYMPHADENOPATHY
                    ↓
┌──────────────────────────────────────────────────────────┐
│              CLINICAL ASSESSMENT                         │
│  - Duration of symptoms                                  │
│  - Classic triad present? (fever, pharyngitis, nodes)   │
│  - Posterior cervical lymphadenopathy? (LR+ 3.1)        │
│  - Splenomegaly?                                        │
│  - Risk factors: Age 15-25, college student, kissing    │
│  - Exposure history                                      │
│  - Red flags: Severe pain, hypotension, stridor         │
└──────────────────────────────────────────────────────────┘
                    ↓
         ┌──────────┴──────────┐
    HIGH SUSPICION         LOW SUSPICION
    (Classic triad         (Atypical features
     + posterior nodes)     or unclear)
         ↓                      ↓
┌──────────────────┐    ┌──────────────────┐
│ INITIAL TESTS:   │    │ BROADER WORKUP:  │
│ - FBC            │    │ - FBC            │
│ - Monospot       │    │ - Throat swab    │
│ - LFTs           │    │ - LFTs           │
└──────────────────┘    │ - HIV test       │
         ↓               │   (if risk)      │
    MONOSPOT TEST       │ - CMV serology   │
         ↓               └──────────────────┘
  ┌──────┴──────┐              ↓
POSITIVE      NEGATIVE    TARGETED TESTS
  ↓               ↓              ↓
DIAGNOSIS    ┌────┴─────┐    BASED ON
             │ TIMING?  │    CLINICAL
             │          │    CONTEXT
             │          │
        ┌────┴────┬─────────┐
     WEEK 1    WEEK 2+   OTHER
        ↓          ↓         ↓
    REPEAT IN   EBV      CONSIDER:
    7-10 DAYS SEROLOGY   - Strep pharyngitis
        ↓          ↓      - CMV (heterophile−)
    POSITIVE  INTERPRET  - HIV (risk factors)
        ↓      VCA/EBNA  - Toxoplasma
    DIAGNOSIS     ↓      - Lymphoma (B symptoms)
              ┌────┴────┐
           ACUTE IM  PAST EBV
           (VCA IgM+  (VCA IgM−
           EBNA−)     EBNA+)
              ↓          ↓
          DIAGNOSIS  ALTERNATIVE
                     DIAGNOSIS

Risk Stratification for Complications

Low Risk (95% of Cases):

• Age 15-25 years
• Classic triad presentation
• No comorbidities
• Spleen non-palpable or less than 2 cm below costal margin
• Platelets > 100 x 10^9/L
• No respiratory compromise
• Normal consciousness

Management: Outpatient; rest, analgesia, activity restriction; return precautions.

Moderate Risk (4% of Cases):

• Age less than 12 or > 40 years
• Spleen palpable 2-4 cm below costal margin
• Platelets 50-100 x 10^9/L
• Moderate thrombocytopenia
• Difficulty swallowing but maintaining hydration
• Mild-moderate hepatitis (ALT 5-10x ULN)

Management: Close outpatient follow-up (2-3 days); repeat examination; phone contact; clear return precautions; consider abdominal ultrasound.

High Risk (1% of Cases):

• Immunocompromised (HIV, transplant, chemotherapy)
• Massive splenomegaly (> 6 cm below costal margin or ultrasound > 20 cm)
• Severe thrombocytopenia (less than 50 x 10^9/L)
• Grade 3-4 tonsillar hypertrophy with dysphagia/stridor
• Severe hepatitis (ALT > 10x ULN or jaundice)
• Neurological symptoms
• Persistent fever > 3 weeks
• Signs of HLH (pancytopenia, ferritin > 10,000)

Management: Admission for monitoring; specialist consultation (hematology, ENT, infectious disease); daily examination; complications workup.

Differential Diagnosis Algorithm

MONONUCLEOSIS-LIKE SYNDROME
(Fever + Pharyngitis + Lymphadenopathy + Atypical Lymphocytes)
                    ↓
            HETEROPHILE TEST
                    ↓
         ┌──────────┴──────────┐
      POSITIVE              NEGATIVE
         ↓                      ↓
    EBV INFECTIOUS      ┌──────────────────┐
    MONONUCLEOSIS       │ AGE less than 12 or > 40?  │
         ↓              └──────┬───────────┘
    CONFIRM:                   ↓
    - Atypical         ┌───────┴────────┐
      lymphocytes    YES              NO
      > 10%             ↓                ↓
    - VCA IgM+    EBV SEROLOGY    CMV/HIV/TOXO
      (if needed)      ↓            SEROLOGY
                  ┌────┴─────┐         ↓
               ACUTE IM  PAST EBV  ┌────┴─────┐
               (VCA IgM+ (VCA IgM− │ CMV IgM+ │
               EBNA−)    EBNA+)    │ HIV Ag/Ab+│
                  ↓         ↓      │ Toxo IgM+│
              DIAGNOSIS  LOOK FOR  └──────────┘
                        OTHER          ↓
                        CAUSES     DIAGNOSIS
                           ↓
                    ┌──────┴──────┐
                ATYPICAL       RISK FACTORS
                LYMPHOCYTES      PRESENT?
                ABSENT             ↓
                    ↓          ┌────┴─────┐
                CONSIDER:    YES         NO
                - Strep        ↓           ↓
                  pharyngitis HIV TEST  LYMPHOMA
                - Adenovirus    ↓       WORKUP
                - Viral URI   ┌─┴─┐       ↓
                              +   −    - LDH
                              ↓   ↓    - Peripheral
                           HIV IM  │      smear
                                  CMV   - Flow
                                        - CT
                                        - Biopsy

Management Flowchart: Suspected Splenic Rupture

ACUTE SEVERE LEFT UPPER QUADRANT PAIN IN PATIENT WITH IM
(Day 4-28 of illness, may extend to day 60)
                    ↓
┌─────────────────────────────────────────────────────┐
│          IMMEDIATE ASSESSMENT (ABCDE)               │
│  - Vital signs: BP, HR, RR, O2 sat                 │
│  - Kehr's sign: Left shoulder pain?                │
│  - Peritoneal signs: Guarding, rebound?            │
│  - Signs of shock: Hypotension, tachycardia?       │
└─────────────────────────────────────────────────────┘
                    ↓
         ┌──────────┴──────────┐
    HEMODYNAMICALLY        HEMODYNAMICALLY
    UNSTABLE                  STABLE
    (SBP less than 90 mmHg or        (SBP ≥90 mmHg,
     tachycardia > 120,       stable vitals)
     altered consciousness)        ↓
         ↓                   ┌──────────────┐
┌────────────────────┐      │ URGENT CT    │
│ IMMEDIATE:         │      │ ABDOMEN      │
│ 1. Call surgeon    │      │ with IV      │
│ 2. 2x large IV     │      │ contrast     │
│ 3. Crystalloid     │      └──────────────┘
│    bolus (1-2 L)   │            ↓
│ 4. Cross-match     │      ┌─────┴─────┐
│    6 units RBC     │   RUPTURE   NO RUPTURE
│ 5. Transfuse if    │   CONFIRMED (Splenic
│    Hb less than 70 g/L      │      ↓      infarction,
│ 6. FAST ultrasound │  ┌────┴────┐ hematoma)
│    bedside         │ GRADE I-II GRADE III-V│
│ 7. EMERGENCY       │ (Hematoma, (Laceration,│
│    LAPAROTOMY      │  capsule    free fluid)│
│                    │  intact)        ↓
│ OPERATING ROOM     │      ↓      SURGERY
│ - Splenectomy      │  CONSIDER:  CONSULT
│   (definitive)     │  - Serial       ↓
│ - Splenic artery   │    imaging  DECISION:
│   ligation (rare)  │  - Admit    - Non-op
└────────────────────┘  - Observe    (selected
         ↓                  ↓          stable
POST-SPLENECTOMY     OBSERVATION     Grade I-II)
CARE:                ICU/HDU        - Splenectomy
- Vaccinate:             ↓             (Grade III-V
  Pneumococcal      MONITOR:            or unstable)
  HIB, Meningo      - Vitals Q1-2H       ↓
- Abx prophylaxis - Serial Hb    POST-OPERATIVE
  Penicillin V    - Repeat CT     MANAGEMENT
  lifelong          if deteriorate
- Medical alert       ↓
  bracelet       IF STABLE 48H:
- OPSI education  Discharge with
                  activity restriction

Return to Activity Protocol

GRADUATED RETURN TO ACTIVITY AFTER INFECTIOUS MONONUCLEOSIS

WEEK 0-2: ACUTE PHASE
├─ Activities: Rest at home; minimal exertion
├─ Work/School: Off work/school
├─ Exercise: NONE
├─ Contact Sports: AVOID
└─ Assessment: Monitor symptoms; hydration

WEEK 2-3: EARLY CONVALESCENCE
├─ If fever resolved + able to eat/drink:
│   ├─ Activities: Light activities at home (walking 10-15 min)
│   ├─ Work/School: May return if non-physical job; reduced hours
│   ├─ Exercise: Gentle walking only
│   ├─ Contact Sports: AVOID
│   └─ Assessment: Examine spleen weekly
│
└─ If fever persists or severe fatigue:
    └─ Continue rest; reassess in 1 week

WEEK 3-4: CONVALESCENCE
├─ If symptoms improving:
│   ├─ Activities: Gradual increase; return to usual non-physical activities
│   ├─ Work/School: Full return if sedentary job; modified if physical
│   ├─ Exercise: Light cardio (walking, cycling 20-30 min); avoid contact
│   ├─ Contact Sports: STILL AVOID
│   └─ Assessment: Examine abdomen; ensure spleen regressing
│
└─ If symptoms persist:
    └─ Continue light activities; reassess for complications

WEEK 4-6: LATE CONVALESCENCE
├─ CRITICAL ASSESSMENT:
│   ├─ Examine spleen: Must be non-palpable for contact sports
│   ├─ Symptoms: Should be mostly resolved
│   └─ Fatigue: May still be present but improving
│
├─ NON-CONTACT ATHLETES:
│   └─ May resume: Running, swimming, cycling, golf, tennis (singles)
│
├─ CONTACT ATHLETES:
│   ├─ WEEK 4: Still avoid contact sports
│   ├─ WEEK 5-6: If spleen non-palpable + asymptomatic:
│   │   └─ May consider gradual return to non-contact training
│   └─ WEEK 6-8: Return to contact sports if:
│       ├─ Spleen non-palpable on exam
│       ├─ Asymptomatic for ≥2 weeks
│       └─ Competitive athletes: Ultrasound confirms spleen less than 13 cm
│
└─ HIGH-RISK ATHLETES (rugby, martial arts, wrestling):
    └─ Consider waiting 8 weeks + ultrasound clearance

WEEK 6-8: FULL RECOVERY
├─ Most patients: Fully recovered; all activities permitted
├─ Contact sports: Cleared if spleen non-palpable
├─ Persistent fatigue (10-20%): Graded exercise therapy; CBT referral
└─ Follow-up: Final check at 8 weeks; LFTs should be normal

PERSISTENT SYMPTOMS > 6 MONTHS:
├─ Assess for:
│   ├─ Chronic active EBV (check EBV viral load)
│   ├─ Depression/anxiety
│   ├─ Other causes: Anemia, hypothyroidism, sleep apnea
│   └─ Post-viral fatigue syndrome (most common)
│
└─ Management:
    ├─ Graded exercise therapy (GET)
    ├─ Cognitive behavioral therapy (CBT)
    ├─ Symptom management
    └─ Reassurance + patient education

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15. Laboratory Interpretation Pearls

Interpreting the Complete Blood Count in IM

White Blood Cell Count:

Key Points:

• Total WBC may be normal or mildly elevated in first week (don't exclude IM).
• Absolute lymphocyte count > 4.5 x 10^9/L is more specific than percentage.
• Atypical lymphocytes > 10% highly suggestive (sensitivity 75%, specificity 92%).
• Neutropenia may occur transiently; if severe/persistent, consider complications.

Atypical Lymphocyte (Downey Cell) Identification:

CRITICAL: Downey Type III can mimic leukemic blasts. Differentiating features:

• IM atypical lymphocytes: Mature lymphocyte features, irregular cytoplasm, heterogeneous population, clinical context (fever, pharyngitis, nodes).
• Leukemic blasts: Immature nuclear chromatin, nucleoli, monomorphic population, no pharyngitis/nodes, persistent findings, +/− anemia/thrombocytopenia.
• If uncertain: Flow cytometry (atypical lymphocytes are mature T cells CD3+ CD8+; blasts have immature markers).

Interpreting EBV Serology: Advanced Scenarios

Scenario 1: All Negative (VCA IgM−, VCA IgG−, EBNA−)

• Interpretation: Seronegative; never infected with EBV; susceptible.
• Clinical Action: IM excluded; look for alternative diagnoses (CMV, toxoplasma, HIV, strep).
• Note: 5-10% of adults remain EBV-seronegative; higher risk of symptomatic IM if infected later.

Scenario 2: VCA IgM+, VCA IgG+, EBNA−

• Interpretation: Acute primary EBV infection (diagnostic of IM).
• Timing: Days 7-21 of illness typically.
• Clinical Action: Confirms IM; no further testing needed.

Scenario 3: VCA IgM−, VCA IgG+, EBNA+

• Interpretation: Past EBV infection; immune; NOT acute IM.
• Clinical Action: Look for alternative cause of symptoms (CMV, HIV, lymphoma).
• Note: This is the most common serological pattern in general population (> 90% of adults).

Scenario 4: VCA IgM+, VCA IgG+, EBNA+

• Interpretation: Recent infection (convalescent phase, 3-6 months post-acute) OR false positive VCA IgM OR reactivation.
• Clinical Action:
  • "If consistent with recent IM (symptoms 1-3 months ago): Convalescent IM."
  • "If no recent IM symptoms: Likely false positive IgM (test cross-reactivity); past infection."
  • "If immunocompromised: Consider reactivation; check EBV PCR viral load."

Scenario 5: VCA IgM−, VCA IgG+, EBNA−

• Interpretation: Indeterminate; may represent:
  • (a) Very early acute infection (IgM not yet developed, day 1-7).
  • (b) Waning antibody after acute infection (EBNA slow to develop in some, 10-20%).
  • (c) False negative EBNA (rare assay failure).
• Clinical Action:
  • "If acute symptoms: Repeat serology in 2-3 weeks (expect EBNA+ if past infection, or VCA IgM+ if early acute)."
  • "If chronic symptoms: Check EBV PCR viral load (exclude chronic active EBV)."

Scenario 6: VCA IgM+, VCA IgG−, EBNA−

• Interpretation: Very rare; possible very early infection (seroconversion window) OR false positive IgM.
• Clinical Action: Repeat serology in 1-2 weeks (expect VCA IgG to appear if true acute infection).

Scenario 7: High EA-D IgG with VCA IgG+ EBNA+

• Interpretation: Possible EBV reactivation (EA-D = early antigen, diffuse; indicates lytic replication).
• Clinical Action:
  • "If immunocompetent: Usually asymptomatic reactivation; no treatment needed."
  • "If immunocompromised: Check EBV PCR viral load; consider antiviral therapy or reduced immunosuppression."

Liver Function Test Patterns in IM

When to Escalate:

• ALT/AST > 10x ULN: Check hepatitis A/B/C, autoimmune markers, paracetamol level.
• Bilirubin > 100 μmol/L (6 mg/dL): Imaging (ultrasound) to exclude biliary obstruction.
• INR > 1.5 or encephalopathy: Acute liver failure; urgent hepatology/transplant center referral.
• Persistent elevation > 8 weeks: Re-evaluate; exclude chronic hepatitis, autoimmune hepatitis.

Recovery:

• 95% normalize by 4-8 weeks.
• Follow weekly until normal.
• Avoid hepatotoxic drugs during acute phase.
• Moderate alcohol restriction until normalization.

Ultrasound Findings and Splenic Measurements

Normal Splenic Dimensions:

• Craniocaudal length: 8-13 cm (upper limit normal).
• Thickness: less than 4 cm.
• Weight: 150-200 g.

IM Splenomegaly Grading:

Ultrasound Red Flags:

• Subcapsular hematoma: Hypoechoic or anechoic rim around spleen; increased rupture risk; admit for observation.
• Splenic infarction: Wedge-shaped hypoechoic areas; correlate with LUQ pain; conservative management unless extensive.
• Free fluid (ascites/blood): Suggests rupture or bleeding; urgent CT and surgical consultation.

Indications for Ultrasound in IM:

1. Clinical splenomegaly (palpable): Document size for return-to-activity decision.
2. Competitive/high-risk athletes: Baseline and clearance scans before contact sports.
3. Abdominal pain: Exclude subcapsular hematoma or infarction.
4. Prolonged course: If spleen still palpable at 6-8 weeks, document size and trend.
5. Uncertain palpation: If examination unclear but need to make return-to-sport decision.

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16. Special Populations

Infectious Mononucleosis in Children (less than 12 Years)

Epidemiology:

• Primary EBV infection often asymptomatic or mild URI-like illness (50-70%).
• Symptomatic IM less common than adolescents but does occur.
• Earlier seroconversion in lower socioeconomic settings (daycare, crowded housing).

Clinical Differences:

• Less pharyngitis: Sore throat less prominent; may present with fever + rash.
• More abdominal symptoms: Vomiting, diarrhea, abdominal pain more common.
• Rash: Spontaneous rash more common (15-20% vs. 10% in adults).
• Hepatosplenomegaly: Proportionally more common.
• Fever: May be only presenting symptom.

Diagnostic Challenges:

• Heterophile antibody test: Sensitivity only 50-70% in children less than 12 years (vs. 85-90% adults).
• False negatives common: Proceed to EBV serology (VCA IgM, VCA IgG, EBNA) if heterophile negative.
• Differential diagnosis broader: Include other childhood exanthems (measles, rubella, roseola, fifth disease).

Management:

• Supportive care as in adults.
• Activity restriction: Avoid rough play, contact sports for 4-6 weeks if splenomegaly.
• Ampicillin/amoxicillin: Still avoid (rash occurs in children too).
• Paracetamol dosing: 15 mg/kg PO Q4-6H (max 75 mg/kg/day or 4 g/day).
• Ibuprofen dosing: 10 mg/kg PO Q6-8H (max 40 mg/kg/day).

Prognosis:

• Generally excellent; shorter illness duration than adolescents (1-2 weeks vs. 2-4 weeks).
• Post-viral fatigue less common in children.

Infectious Mononucleosis in Older Adults (> 40 Years)

Epidemiology:

• Uncommon (5-10% of IM cases) since most adults already seropositive.
• Primary infection in seronegative middle-aged/older adults.
• May represent reactivation in immunosenescence.

Clinical Differences:

• Less pharyngitis: Sore throat less prominent (50% vs. 80-90% in adolescents).
• More hepatitis: Jaundice more common (15-20% vs. 5-10%); transaminitis higher.
• Prolonged fever: Fever > 3 weeks more common; may present as fever of unknown origin (FUO).
• Less lymphadenopathy: Nodes less prominent; may be absent.
• Atypical presentation: Often lacks classic triad; diagnosis more challenging.

Diagnostic Challenges:

• Heterophile antibody: Lower sensitivity (70-80% vs. 85-90% in young adults).
• Differential diagnosis critical: Must exclude malignancy (lymphoma, leukemia), autoimmune disease, other infections.
• Higher threshold to consider alternative diagnoses: HIV, CMV, toxoplasma, lymphoma.

Investigations:

• Always obtain EBV serology (VCA IgM) even if heterophile positive (confirm diagnosis).
• Broader workup: HIV test, CMV serology, LDH (elevated in lymphoma), peripheral smear (exclude blasts), imaging if lymphadenopathy massive.

Management:

• Supportive care as in younger adults.
• Higher vigilance for complications: Hepatic failure (rare but higher risk), neurological complications.
• Activity restriction: Splenomegaly still requires 4-8 week contact sport avoidance (though older adults less likely to engage in contact sports).

Prognosis:

• Generally good but recovery may be slower (4-8 weeks vs. 2-4 weeks).
• Post-viral fatigue more common and prolonged (20-30% vs. 10-20% in young adults).
• Higher morbidity from complications if they occur.

Infectious Mononucleosis in Pregnancy

Epidemiology:

• Rare (most women of childbearing age already EBV-seropositive).
• Primary infection in 1-5 per 10,000 pregnancies.

Maternal Effects:

• Symptoms same as non-pregnant women; classic triad.
• Pregnancy does NOT increase severity or complication risk (unlike influenza, varicella).
• Diagnosis and management unchanged.

Fetal/Neonatal Effects:

• Transplacental transmission: Very rare (less than 5% of primary infections during pregnancy).
• Congenital infection: Extremely rare; most cases asymptomatic.
• No congenital syndrome: Unlike CMV, rubella, toxoplasma, parvovirus, EBV does NOT cause congenital malformations or fetal hydrops.
• Neonatal outcome: Generally excellent; no increased risk of miscarriage, stillbirth, or congenital anomalies.

Management:

• Supportive care: As in non-pregnant women; rest, hydration, analgesia (paracetamol safe in pregnancy).
• Avoid NSAIDs: Especially third trimester (risk of premature ductus arteriosus closure).
• Activity restriction: Still important; avoid heavy lifting, contact sports.
• Antivirals NOT recommended: Aciclovir pregnancy category B but no proven benefit in IM.
• Fetal monitoring: Routine prenatal care; ultrasound as per standard obstetric protocol; no additional monitoring needed for EBV.

Delivery:

• No contraindication to vaginal delivery.
• If acute IM at delivery, use standard precautions (EBV in saliva, not genital secretions).

Breastfeeding:

• Safe: EBV may be present in breast milk but breastfeeding NOT contraindicated.
• Most neonates exposed via breast milk remain asymptomatic or develop mild infection with maternal antibody protection.

Counseling:

• Reassure: EBV primary infection in pregnancy does NOT carry same risks as CMV, rubella, toxoplasma.
• Prognosis: Excellent for mother and baby.
• Future pregnancies: Immune after primary infection; no risk of reactivation harming future pregnancies.

Infectious Mononucleosis in Immunocompromised Patients

At-Risk Populations:

• HIV/AIDS (especially CD4 less than 200 cells/μL).
• Solid organ transplant recipients (on immunosuppression).
• Hematopoietic stem cell transplant recipients.
• Chemotherapy patients (lymphoma, leukemia).
• Primary immunodeficiencies (SCID, XLP, CVID).
• Chronic corticosteroid use (> 20 mg prednisone daily for > 2 weeks).
• Biologic therapy (rituximab, TNF-inhibitors).

Clinical Differences:

• Severe/prolonged illness: Symptoms more severe, longer duration (weeks to months).
• Higher viral load: EBV PCR often very high (> 10^5-10^6 copies/mL).
• Atypical presentations: May lack fever, pharyngitis; present with isolated lymphadenopathy or hepatosplenomegaly.
• Higher complication rate: HLH (5-10% vs. less than 0.5%), neurological (5-10% vs. 1-5%), chronic active EBV.

Diagnostic Approach:

• EBV PCR (viral load): Essential; quantitate baseline and monitor.
• Heterophile antibody: Less reliable (may be false negative due to impaired B-cell function).
• EBV serology: May be difficult to interpret; IgM response may be blunted.
• Tissue biopsy: If atypical lymphadenopathy (exclude PTLD, lymphoma); stain for EBV (EBER in situ hybridization).

Complications to Monitor:

• Post-Transplant Lymphoproliferative Disease (PTLD): EBV-driven B-cell proliferation; 1-20% of transplant recipients; presents as lymphadenopathy, mass lesions (GI, CNS, lung); diagnose with biopsy; treat with reduced immunosuppression + rituximab +/− chemotherapy.
• Chronic Active EBV (CAEBV): Prolonged symptoms, high viral load, organ involvement; mortality 50-90% without HSCT.
• Hemophagocytic Lymphohistiocytosis (HLH): 5-10% in immunocompromised vs. less than 0.5% immunocompetent; high mortality; requires HLH protocol.
• Opportunistic co-infections: CMV reactivation, fungal infections, PJP; maintain broad differential.

Management:

• Antiviral therapy: Consider ganciclovir/valganciclovir or foscarnet (though efficacy uncertain; inhibit lytic replication but not latency).
  • "Ganciclovir: 5 mg/kg IV Q12H for 14-21 days."
  • "Valganciclovir: 900 mg PO BID for 14-21 days."
• Reduce immunosuppression: If transplant patient, reduce tacrolimus, MMF, prednisone (balance rejection risk vs. EBV control); consult transplant team.
• IVIG: 0.4-1 g/kg IV; may provide passive immunity and immune modulation; evidence weak but often tried.
• Rituximab: Anti-CD20 monoclonal antibody; depletes B cells (EBV reservoir); used for PTLD; dose 375 mg/m² IV weekly x4 weeks.
• Monitor EBV viral load: Weekly PCR; rising viral load indicates inadequate control; falling indicates improvement.
• Prophylaxis: After resolution, some centers use valganciclovir prophylaxis to prevent PTLD in high-risk transplant recipients.

Prognosis:

• Variable: Depends on degree of immunosuppression and ability to restore immunity.
• PTLD: 50-80% respond to reduced immunosuppression + rituximab; 20-50% require chemotherapy; mortality 10-30%.
• CAEBV: Requires HSCT for cure; 5-year survival post-HSCT 50-70%.

Infectious Mononucleosis in Athletes

Unique Considerations:

• Competitive athletes have high stakes for return to play (team obligations, scholarships, professional contracts).
• Contact sport athletes (American football, rugby, hockey, wrestling, martial arts) at highest splenic rupture risk.
• Pressure to return early; need objective criteria for clearance.

Clinical Evaluation:

• Baseline assessment: Spleen size at presentation (palpation + ultrasound).
• Weekly monitoring: Examine abdomen weekly; document spleen size.
• Symptom resolution: Must be asymptomatic (no fever, pharyngitis resolved, normal energy) before considering return.

Return-to-Play Protocol:

Phase 1 (Weeks 0-3): Complete Rest

• No athletic activity.
• Light walking for daily activities only.
• Monitor symptom resolution and spleen size.

Phase 2 (Week 3-4): Light Aerobic Activity

• If: Spleen less than 2 cm palpable or non-palpable; symptoms resolved.
• Activities: Walking, stationary cycling, light jogging (20-30 min); 50-70% max HR.
• Monitor: No abdominal pain, no increase in spleen size.

Phase 3 (Week 4-5): Moderate Training

• If: Spleen non-palpable on exam; symptom-free.
• Activities: Running, swimming, cycling (full intensity); sport-specific drills (non-contact).
• Ultrasound: Obtain at week 4-5 (must be less than 13 cm craniocaudal).

Phase 4 (Week 5-6): Non-Contact Practice

• If: Ultrasound less than 13 cm; non-palpable; asymptomatic ≥2 weeks.
• Activities: Full practice without contact; conditioning; skill work.

Phase 5 (Week 6-8): Return to Full Contact

• If: Spleen less than 13 cm on ultrasound; non-palpable; asymptomatic ≥4 weeks.
• Activities: Full contact practice; competitive play.
• Note: Some team physicians require 8 weeks regardless; very conservative approach for high-collision sports (American football, rugby).

High-Risk Sports (May require longer clearance):

• Rugby, American football, ice hockey, lacrosse, martial arts, wrestling, boxing.
• Consider: 8-week minimum, repeat ultrasound at 6 and 8 weeks, medical clearance by team physician + athletic trainer + player.

Shared Decision-Making:

• Discuss risks: 0.1-0.5% splenic rupture; 9-13% mortality if rupture; potential career-ending injury.
• Athlete preference: Balance return-to-play desire vs. safety.
• Document: Shared decision-making, informed consent, medical clearance in writing.

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17. Public Health and Prevention

Transmission Prevention

Healthcare Settings:

• Isolation: Not routinely required (IM patients not highly contagious via droplet/airborne routes).
• Standard Precautions: Hand hygiene, avoid direct contact with saliva/secretions.
• Healthcare workers with IM: Should avoid patient care during acute illness (first 1-2 weeks) to prevent transmission and allow recovery.
• Equipment: Clean and disinfect shared thermometers, stethoscopes, otoscopes after use.

Community Settings:

• School/Workplace: Patients can return when fever resolved and able to participate in activities; no mandatory exclusion period.
• Daycare: Children with IM do not require exclusion once well enough to participate; emphasize hygiene (no sharing bottles, utensils).
• College dormitories: High-transmission setting; educate on avoiding sharing drinks, utensils, kissing during acute illness; encourage ill students to stay in room during acute phase.

Personal Measures:

• Avoid sharing: Drinks, utensils, toothbrushes, lipstick, cigarettes during acute illness and for 6-18 months (period of viral shedding).
• Kissing: Avoid intimate kissing during acute illness; partners may already be seropositive; inform partners of diagnosis.
• Hand hygiene: Wash hands after touching mouth, before eating, after coughing/sneezing.
• Cough etiquette: Cover coughs/sneezes with elbow, not hands.

Vaccine Development

Current Status:

• No licensed vaccine available as of 2026.
• Multiple vaccine candidates in preclinical and early clinical trials.

Vaccine Strategies:

• gp350-based vaccines: Target EBV glycoprotein gp350 (binds CD21 on B cells); prevents infection or reduces disease severity.
  • "Phase I/II trials: Some candidates show immunogenicity and antibody responses; no efficacy trials completed yet."
• Multi-antigen vaccines: Include latent (EBNA1, LMP2) and lytic (gp350, BZLF1) antigens; aim to prevent infection AND control latency.
• Therapeutic vaccines: For immunocompromised patients; boost T-cell immunity to control EBV reactivation and prevent PTLD.

Challenges:

• EBV is ubiquitous; 90-95% of adults already infected (vaccine needed in children before exposure).
• Latency: Vaccine must prevent establishment of latent infection (difficult).
• Oncogenicity: Vaccine must not increase malignancy risk.
• Target populations: Adolescents (prevent IM), transplant recipients (prevent PTLD), endemic NPC populations (prevent cancer).

Timeline:

• Optimistic projections: Licensed vaccine may be available 2030-2035 (still 5-10 years away).

Epidemiological Surveillance

Notifiable Disease:

• IM is NOT a notifiable disease in most countries (unlike measles, hepatitis, HIV).
• Surveillance relies on sentinel physician networks, hospital databases.

Epidemiology Trends:

• Delayed infection: In developed countries, primary infection increasingly delayed to adolescence/adulthood (vs. early childhood in past).
• Hygiene hypothesis: Improved hygiene, less crowding → later EBV seroconversion → more symptomatic IM cases in adolescents.
• Incidence stable: Overall incidence of IM in adolescents has remained relatively stable (45-50 per 100,000 annually).

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Medical Disclaimer: MedVellum content is for educational purposes and clinical reference. Clinical decisions should account for individual patient circumstances. Always consult appropriate specialists and adhere to local guidelines and protocols.