Infectious mononucleosis

Overview 
Theory 
Diagnosis 
Management 
Follow up 
Resources 

Last reviewed: 24 May 2025

Last updated: 16 Nov 2021

Infectious mononucleosis is characterised by the classic triad of fever, pharyngitis, and lymphadenopathy, along with atypical lymphocytosis. It is often subclinical in young children.

Caused by infection with Epstein-Barr virus (EBV) in 80% to 90% of cases. Positive heterophile antibody test and serological test for antibodies against EBV are usually diagnostic.

Rare but potentially life-threatening complications include severe upper airway obstruction, splenic rupture, fulminant hepatitis, encephalitis, severe thrombocytopaenia, and haemolytic anaemia.

Treatment is usually symptomatic.

Definition

Infectious mononucleosis (IM), also known as glandular fever, is a clinical syndrome most commonly caused by Epstein-Barr virus (EBV) infection in 80% to 90% of cases.[1][2] Other causes are much less common. The diagnosis 'infectious mononucleosis' is primarily used when the syndrome is caused by EBV; 'mononucleosis syndrome' should be used when the syndrome is caused by a non-EBV aetiology. This topic focuses on IM caused by EBV.

IM typically manifests in adolescents and young adults as a febrile illness with sore throat and enlarged lymph nodes. Atypical lymphocytosis and a positive heterophile antibodies test are usually observed. The disease is generally mild in children, but more severe in adults. Resolution of the acute illness is usually followed by a lifelong latent infection, with over 90% of the adult population infected worldwide.[3]

History and exam

Key diagnostic factors

presence of risk factors
fever
pharyngitis
cervical or generalised lymphadenopathy
malaise

Full details

Other diagnostic factors

splenomegaly
rash
signs of hepatitis (hepatomegaly, jaundice)
jaundice
myalgia

Full details

Risk factors

kissing
sexual behaviour

Full details

Diagnostic investigations

1st investigations to order

FBC
heterophile antibodies
Epstein-Barr virus (EBV)-specific antibodies
LFTs

Full details

Investigations to consider

real-time polymerase chain reaction (PCR)
ultrasonography of abdomen
CT of abdomen

Full details

Treatment algorithm

ACUTE

all patients

Contributors

Authors

George Turabelidze, MD, PhD

Medical Epidemiologist

Missouri Department of Health and Senior Services

Adjunct Assistant Professor of Clinical Pediatrics

Washington University School of Medicine

St Louis

Disclosures

GT declares that he has no competing interests.

Peer reviewers

Linda Kalilani, MBBS, MPhil, PhD

Epidemiologist

College of Medicine

University of Malawi

Zomba

Malawi

Disclosures

LK declares that she has no competing interests.

Paul G. Auwaerter, MD, MBA, FACP, FIDSA

Clinical Director

Division of Infectious Diseases

Associate Professor of Medicine

Divisions of Infectious Diseases and General Internal Medicine

Johns Hopkins University School of Medicine

Baltimore

Disclosures

PGA declares that he has no competing interests.

References

Our in-house evidence and editorial teams collaborate with international expert contributors and peer reviewers to ensure that we provide access to the most clinically relevant information possible.

Key articles

Vetsika EK, Callan M. Infectious mononucleosis and Epstein-Barr virus. Expert Rev Mol Med. 2004 Nov 5;6(23):1-16. Abstract

Katz BZ. Update on chronic fatigue syndrome and Epstein-Barr virus. Pediatr Ann. 2002 Nov;31(11):741-4. Abstract

Ganzel TM, Goldman JL, Padhya TA. Otolaryngologic clinical patterns in pediatric infectious mononucleosis. Am J Otolaryngol. 1996 Nov-Dec;17(6):397-400. Abstract

De Paor M, O'Brien K, Fahey T, et al. Antiviral agents for infectious mononucleosis (glandular fever). Cochrane Database Syst Rev. 2016 Dec 8;(12):CD011487.Full text Abstract

Reference articles

A full list of sources referenced in this topic is available to users with access to all of BMJ Best Practice.

Differentials
- Group A streptococcal pharyngitis
- Hepatitis A
- Acute HIV infection
More Differentials
Patient information
Glandular fever (infectious mononucleosis)
More Patient information
Videos
Venepuncture and phlebotomy animated demonstration
Peripheral venous cannulation animated demonstration
More videos
Log in or subscribe to access all of BMJ Best Practice

Use of this content is subject to our disclaimer

Infectious mononucleosis

Summary

Definition

History and exam

Key diagnostic factors

Other diagnostic factors

Risk factors

Diagnostic investigations

1st investigations to order

Investigations to consider

Treatment algorithm

all patients

Contributors

Authors

George Turabelidze, MD, PhD

Disclosures

Peer reviewers

Linda Kalilani, MBBS, MPhil, PhD

Disclosures

Paul G. Auwaerter, MD, MBA, FACP, FIDSA

Disclosures

References

Key articles

Reference articles

A full list of sources referenced in this topic is available to users with access to all of BMJ Best Practice.

Differentials

Patient information

Videos

Log in or subscribe to access all of BMJ Best Practice

Log in or subscribe to access all of BMJ Best Practice

Log in to access all of BMJ Best Practice