Overview
Infectious mononucleosis (glandular fever) is a viral illness caused by Epstein-Barr virus (EBV). It most commonly affects teenagers and young adults, presenting with severe fatigue, sore throat, fever, and swollen lymph nodes. Most people recover fully within 2 to 6 weeks, though fatigue can persist for months. Almost all adults have been infected with EBV by age 40.
How common is it?
Glandular fever is very common. The incidence in the UK is approximately 40 to 50 per 100,000 per year, with peak incidence in 15 to 25-year-olds. In less developed settings, primary infection occurs in childhood and is mostly asymptomatic.
Causes and risk factors
EBV (Human Herpesvirus 4) is transmitted primarily through saliva. The virus infects B lymphocytes and causes a marked T-lymphocyte response responsible for most clinical features.
Common risk factors
- Close contact with saliva of an infected person (kissing disease)
- Sharing drinks, utensils, or food
- Teenagers and young adults most susceptible (primary EBV infection in childhood is usually mild)
- Immunosuppressed individuals: severe or prolonged illness
Symptoms
- Severe sore throat (often the most prominent symptom, with white exudate on tonsils)
- Profound fatigue
- High fever
- Grossly swollen lymph nodes, especially at the back of the neck
- Splenomegaly (enlarged spleen) in 50 to 60%
- Hepatomegaly and mild jaundice in 5 to 10%
- Morbilliform (measles-like) rash if ampicillin or amoxicillin given erroneously
When to see a doctor
Seek immediate assessment for severe breathlessness (large tonsils obstructing the airway), left-sided abdominal pain (splenic rupture — rare emergency), or signs of liver failure. Contact sports should be avoided until splenomegaly resolves.
Diagnosis
Blood film shows atypical lymphocytes (Downey cells). Monospot test (heterophile antibody) is positive in about 85% of cases. EBV-specific antibodies (VCA IgM, EA, EBNA) confirm diagnosis when monospot is negative. Raised liver enzymes common.
Treatments
Supportive care
Rest during the acute illness, adequate fluid intake, and paracetamol or ibuprofen for fever and sore throat. No specific antiviral treatment is recommended for uncomplicated cases.
Corticosteroids
A short course of prednisolone is indicated for severe pharyngeal swelling causing airway compromise, severe thrombocytopenia, or neurological complications.
Avoidance of contact sports
Contact sports and vigorous exercise should be avoided for at least 3 to 4 weeks from the onset of illness to reduce the very small risk of splenic rupture.
Self-care and lifestyle
- Rest as much as needed — pushing through fatigue prolongs recovery
- Avoid alcohol (liver involvement is common)
- Do not take amoxicillin or ampicillin (causes a dramatic rash in 90% with glandular fever)
- Avoid contact sport until splenomegaly confirmed to have resolved
Prevention
There is no vaccine against EBV. Avoiding close contact with known active cases is impractical given the wide prevalence and infectious period. Good hygiene reduces transmission.