Electrolytes including sodium and potassium for dehydration
Repletion guided by clinical status
Avoid hypotonic fluids for significant dehydration
Pregnancy and bleeding context
Urine or serum pregnancy test in pregnancy capable patients
Guides imaging choices for abdominal pain
Ensures safe medication selection
Hemorrhage suspicion
Type and screen for suspected splenic injury or significant bleeding
Crossmatch if unstable
Serial hemoglobin if ongoing concern
PITFALLS
Lab interpretation pitfalls
Normal CBC does not exclude early infectious mononucleosis
Transaminase elevation is nonspecific and may reflect alternate hepatitis etiologies
Diagnostic Tests
Scoring Systems
Clinical criteria and decision support
Infectious mononucleosis clinical suspicion features
Posterior cervical lymphadenopathy
Fatigue with prolonged course
Palatal petechiae
Streptococcal pharyngitis decision tools are not diagnostic for EBV
Centor or McIsaac can guide strep testing decisions
Co infection possible
No validated scoring system reliably predicts splenic rupture risk
Activity restriction based on time course and clinical recovery
Imaging does not reliably clear early return to contact sports
MRI
MRI role
Not routine for uncomplicated infectious mononucleosis
Limited availability and low yield in typical presentations
Reserve for focal neurologic complication evaluation
CNS complication contexts
Encephalitis
Myelitis
CT
CT indications
Suspected splenic rupture or intraabdominal hemorrhage
Contrast CT abdomen and pelvis if stable
Surgical consultation should not be delayed if unstable
Deep neck infection concern
CT neck with contrast for peritonsillar or retropharyngeal abscess concern
Consider airway risk before transport
Ultrasound
Ultrasound applications
Focused assessment for free fluid if hemodynamic instability with abdominal pain
Positive free fluid increases urgency for surgical evaluation
Negative study does not exclude splenic injury
Spleen assessment limitations
Splenomegaly measurement does not reliably predict rupture risk
Do not use spleen size alone to authorize contact sport return
Ultrasound pregnancy pathway
Pelvic ultrasound if abdominal pain with positive pregnancy test
Ectopic pregnancy exclusion
Disposition
Admission and higher level of care
Admission indications
Airway compromise or impending obstruction
Stridor
Inability to tolerate oral intake
Severe dehydration
Failed oral challenge after antiemetic and analgesia
Significant electrolyte abnormalities
Significant hematologic complications
Severe thrombocytopenia with bleeding
Hemolytic anemia with symptoms or instability
Suspected splenic rupture
Hemodynamic instability
Peritoneal signs
Significant hepatitis with concern for liver failure
Encephalopathy
Coagulopathy concern
Discharge criteria and follow up
Discharge suitability
No airway risk
Adequate oral intake and pain control
Reliable return precautions and follow up
Follow up plan
Primary care follow up within 3 to 7 days if persistent symptoms
Return to sports clearance pathway
Symptom resolution
Shared decision making for timing
Treatment
Supportive care
Hydration and nutrition
Oral hydration strategies
Frequent small volumes
Electrolyte solutions if vomiting or diarrhea
IV fluids for dehydration
0.9% sodium chloride 10 to 20 mL/kg bolus
Reassess after each bolus
Repeat as needed based on perfusion and urine output
Analgesia and antipyresis
Acetaminophen
15 mg/kg PO q6h PRN
Maximum 60 mg/kg/day
Adult maximum 3000 mg/day when outpatient
Ibuprofen
10 mg/kg PO q6h to q8h PRN
Maximum 40 mg/kg/day
Adult maximum 2400 mg/day OTC aligned dosing
Avoid acetaminophen overdose in hepatitis
Use lowest effective dose
Review combination cold products
Corticosteroids and escalation therapies
Steroids are not routine for uncomplicated infectious mononucleosis
Evidence quality mixed and routine symptom benefit not established
Use limited to severe complications
Indications for corticosteroids
Impending airway obstruction from tonsillar hypertrophy
Dexamethasone 10 mg IV or IM once
Pediatrics 0.6 mg/kg IV or IM once
Maximum 10 mg
Prednisone 40 to 60 mg PO daily for 3 to 5 days as alternative
Taper usually not required for short course
Severe hemolytic anemia or severe thrombocytopenia
Prednisone 1 mg/kg/day PO
Hematology consultation for duration and taper
IVIG consideration if refractory thrombocytopenia
Antimicrobials and co infection
Antibiotics only for proven bacterial co infection
Group A streptococcal pharyngitis positive testing
Penicillin V 500 mg PO BID for 10 days
Pediatric dosing per weight based local standard
Avoid in true penicillin allergy
Cephalexin 500 mg PO BID for 10 days if non anaphylactic penicillin allergy
Avoid if immediate hypersensitivity history
Azithromycin 500 mg PO day 1 then 250 mg PO daily days 2 to 5 if anaphylactic beta lactam allergy
Local resistance considerations
QT risk review
Avoid aminopenicillins in suspected EBV infection
Amoxicillin associated rash common in EBV
Rash is not reliably a true IgE mediated allergy
Activity restriction and prevention
Splenic rupture risk mitigation
No contact sports and no collision activities for at least 3 weeks from symptom onset
Longer restriction if persistent symptoms
Shared decision making for return to play
Avoid heavy lifting during early illness
Increased intraabdominal pressure risk
Gradual return with symptom guided progression
Transmission reduction
Avoid sharing drinks and utensils
Avoid kissing while symptomatic and early convalescence
Special Populations
Pregnancy
Pregnancy considerations
EBV infection not typically associated with congenital syndrome
Symptom based supportive care remains standard
Avoid unnecessary imaging and medications
Medication safety
Acetaminophen preferred for fever and pain
NSAIDs avoidance in later pregnancy per obstetric guidance
Abdominal pain differential broadened
Ectopic pregnancy
Placental complications if later gestation
Geriatric
Older adult features
Less prominent pharyngitis and lymphadenopathy
Higher likelihood of jaundice and hepatitis pattern
Risk and management considerations
Broader malignancy evaluation if persistent lymphadenopathy
Lower threshold for admission with dehydration and frailty
Pediatrics
Pediatric presentation
Often milder or atypical symptoms in younger children
Adolescents resemble adult presentation
Pediatric management
Weight based dosing for analgesics and steroids
Sports restriction counseling for school athletics
Airway monitoring for significant tonsillar hypertrophy
Background
Epidemiology
Frequency and transmission
EBV is common worldwide and transmitted via saliva
Infectious mononucleosis most common in adolescents and young adults
Coding alignment
ICD-10 infectious mononucleosis
B27.0 gammaherpesviral mononucleosis without complication
B27.9 infectious mononucleosis unspecified
SNOMED CT concept
Infectious mononucleosis
Pathophysiology
Mechanism
EBV infection of B lymphocytes with host immune response
Atypical lymphocytes reflect reactive CD8 T cell response
Organ involvement
Lymphoid tissue hyperplasia
Tonsillar enlargement
Lymphadenopathy
Splenic enlargement from lymphoid hyperplasia
Rupture risk highest early in illness
Hepatic involvement with mild hepatitis
Transaminase elevation common
Therapeutic Considerations
Treatment principles
Supportive care is mainstay
Corticosteroids reserved for severe complications
Evidence and guideline style statements
Routine antibiotics provide no benefit without bacterial co infection
ACEP Level C consensus aligned
Antimicrobial stewardship principle
Activity restriction is recommended to reduce splenic rupture risk
Class I recommendation based on expert consensus
Imaging based clearance is limited by poor correlation with rupture risk
Patient Discharge Instructions
copy discharge instructions
Home care
Rest and fluids
Acetaminophen or ibuprofen as directed on the label or by clinician
Avoid alcohol while liver enzymes are elevated or while symptomatic
Contagion reduction
Avoid kissing and sharing drinks or utensils while sick
Hand hygiene
Activity restriction
No contact sports or collision activities for at least 3 weeks from symptom onset
No heavy lifting during early recovery
Return to sports only when feeling well and cleared if required by team or school
Return to ED now for
Trouble breathing or noisy breathing
Drooling or inability to swallow liquids
Severe worsening throat pain or trismus
Fainting or severe dizziness
New severe abdominal pain or left shoulder pain
Chest pain
Uncontrolled bleeding or widespread bruising
Severe headache, neck stiffness, confusion, or weakness
References
Clinical guidelines and society statements
Core guidance sources
CDC Epstein-Barr virus and infectious mononucleosis clinical overview
AAP Red Book sections on EBV and infectious mononucleosis
IDSA principles for pharyngitis testing and antibiotic stewardship
Evidence grading mapping for this reference
ACEP Level C used for consensus based ED practice where high quality trials are limited
Class I used for broadly accepted safety critical recommendations
Evidence based reviews
Diagnostic testing reviews
Heterophile antibody testing performance varies by illness duration and age
EBV specific serology for heterophile negative cases with high clinical suspicion
Complication literature
Splenic rupture is uncommon but highest risk early in illness
Steroids reserved for airway compromise and severe hematologic complications
SymptomDx is an educational tool for medical professionals. It does not replace clinical judgment. Verify all clinical data and drug dosages with authoritative sources.