What are the symptoms of infectious mononucleosis (mono)?

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From the Guidelines

Mononucleosis (mono) typically presents with a combination of fatigue, sore throat, fever, swollen lymph nodes in the neck and armpits, enlarged spleen, and headache, as noted in patients with chronic active Epstein-Barr virus infection 1. The symptoms of mono can vary in severity and combination, but common symptoms include:

  • Fatigue, which can last for weeks or even months
  • Sore throat, often severe and similar to strep throat
  • Fever
  • Swollen lymph nodes in the neck and armpits
  • Enlarged spleen
  • Headache
  • Body aches
  • Loss of appetite
  • Skin rash Some patients may also develop jaundice (yellowing of the skin and eyes) due to liver involvement 1. The diagnosis of mono usually involves a physical exam and blood tests to confirm the infection, including tests for heterophile antibodies and EBV-specific antibodies, such as IgG and IgM to viral capsid antigen (VCA) and Epstein-Barr nuclear antigen (EBNA) 1. It is essential to seek medical attention if mono is suspected, as proper diagnosis and treatment can help alleviate symptoms and prevent complications, particularly in immunocompromised patients who are at risk of developing lymphoproliferative disease 1.

From the Research

Symptoms of Mono

The symptoms of mono, also known as infectious mononucleosis, can vary from person to person. Some common symptoms include:

  • Fever
  • Tonsillar pharyngitis
  • Lymphadenopathy
  • Fatigue, which can be profound but tends to resolve within three months 2
  • Periorbital and/or palpebral edema, typically bilateral, occurs in one-third of patients 2
  • Splenomegaly and hepatomegaly occur in approximately 50% and 10% of cases, respectively 2
  • A skin rash, which is usually widely scattered, erythematous, and maculopapular, occurs in approximately 10 to 45% of cases 2
  • Sore throat and significant fatigue, palatal petechiae, posterior cervical or auricular adenopathy, marked adenopathy, or inguinal adenopathy 3
  • Atypical lymphocytosis of at least 20 percent or atypical lymphocytosis of at least 10 percent plus lymphocytosis of at least 50 percent 3

Diagnosis and Treatment

Diagnosis of mono is typically made through a combination of physical examination, medical history, and laboratory tests, including:

  • Heterophile antibody test, which has a sensitivity of 87% and specificity of 91% but can have a false-negative result in children younger than five years and in adults during the first week of illness 4
  • Complete blood count with differential to assess for greater than 40% lymphocytes and greater than 10% atypical lymphocytes 4
  • Epstein-Barr viral capsid antigen-antibody testing, which is more sensitive and specific but more expensive and takes longer to process than the rapid heterophile antibody test 4 Treatment of mono is supportive, with a focus on relieving symptoms and managing complications. This may include:
  • Adequate hydration, analgesics, antipyretics, and adequate rest 3
  • Avoiding contact sports or strenuous exercise for 8 weeks or while splenomegaly is still present 2
  • Symptomatic relief, as glucocorticoids and antivirals do not reduce the length or severity of illness 5

Complications and Risks

Mono can increase the risk of certain complications, including:

  • Splenic rupture, which occurs in 0.1 to 0.5% of patients with infectious mononucleosis and is potentially life-threatening 2
  • Airway obstruction, which is the most common cause of hospitalization from IM, especially in children 5
  • Fulminant EBV infection, which is more likely to occur in patients with immunosuppression 5
  • Chronic fatigue syndrome, which is a risk factor for infectious mononucleosis 2
  • Certain cancers, including Hodgkin lymphoma, non-Hodgkin lymphoma, and nasopharyngeal carcinoma, and some autoimmune diseases, which have been linked to Epstein-Barr virus infection 4

References

Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

Research

Infectious Mononucleosis: An Updated Review.

Current pediatric reviews, 2024

Research

Epstein-Barr virus infectious mononucleosis.

American family physician, 2004

Research

Infectious Mononucleosis: Rapid Evidence Review.

American family physician, 2023

Research

Common questions about infectious mononucleosis.

American family physician, 2015

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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