Infectious mononucleosis, also known as glandular fever, is a common cause of a severe sore throat. It is usually caused by the Epstein-Barr virus.


  • Incidence: 70.00 cases per 100,000 person-years
  • Peak incidence: 20-30 years
  • Sex ratio: 1:1
<1 1-5 6+ 16+ 30+ 40+ 50+ 60+ 70+ 80+


Infectious mononucleosis (glandular fever) is caused by the Epstein-Barr virus (EBV, also known as human herpesvirus 4, HHV-4) in 90% of cases. Less frequent causes include cytomegalovirus and HHV-6. It is most common in adolescents and young adults.

There is an interesting correlation between EBV and socioeconomic groups. Lower socioeconomic groups have high rates of EBV seropositivity, having frequently acquired EBV in early childhood when the primary infection is often subclinical. However, higher socioeconomic groups show a higher incidence of infectious mononucleosis, as acquiring EBV in adolescence or early adulthood results in symptomatic disease.

Clinical features

The classic triad of sore throat, pyrexia and lymphadenopathy is seen in around 98% of patients:
  • Sore throat
  • Lymphadenopathy: may be present in the anterior and posterior triangles of the neck, in contrast to tonsillitis which typically only results in the upper anterior cervical chain being enlarged
  • Pyrexia

Other features include:
  • Malaise, anorexia, headache
  • Palatal petechiae
  • Splenomegaly - occurs in around 50% of patients and may rarely predispose to splenic rupture
  • Hepatitis, transient rise in ALT
  • Lymphocytosis: presence of 50% lymphocytes with at least 10% atypical lymphocytes
  • Haemolytic anaemia secondary to cold agglutins (IgM)
  • A maculopapular, pruritic rash develops in around 99% of patients who take ampicillin/amoxicillin whilst they have infectious mononucleosis

Symptoms typically resolve after 2-4 weeks.


  • Heterophil antibody test (Monospot test) - NICE guidelines suggest FBC and Monospot in the 2nd week of the illness to confirm a diagnosis of glandular fever.


Management is supportive and includes:
  • Rest during the early stages, drink plenty of fluid, avoid alcohol
  • Simple analgesia for any aches or pains
  • Consensus guidance in the UK is to avoid playing contact sports for 8 weeks after having glandular fever to reduce the risk of splenic rupture