Infectious mononucleosis (IM) & Epstein-Barr Virus (EBV)

Cause of infectious mononucleosis

Commonest cause – EBV.
Other causes of mononucleosis-like syndrome – CMV, HIV (during seroconversion), Toxoplasma, Hepatitis virus, Adenovirus etc

Epidemiology of IM

Primary EBV infection and infectious mononucleosis are common in children, teenagers and young adults.
95% of healthy individuals are infected with EBV.
In children, infection is usually mild or even asymptomatic.
Symptomatic disease is common in teenagers and young adults (15-24 years).
In adults, the infection is less common, but often severe.

Transmission

It is transmitted via body fluid. Saliva is the commonest mode.
Once infected, an individual can shed the virus in the saliva for approx. 6 months, and intermittently, lifelong.
It is called kissing disease but can be transmitted via less intimate contact than this.
Other modes are – sexual contact and breastfeeding.

Signs and symptoms

Triad of – Fever, tonsillar pharyngitis and lymphadenopathy.
Other common features are – fatigue, splenomegaly (up to 60% cases) and low mood.
You may also find – hepatomegaly, rash, headache and body ache.

Complications

Usually self-limiting disease.
Neurological complications – meningoencephalitis, transverse myelitis, optic neuritis, Cranial nerve palsy, Guillain–Barré syndrome.
Haematological complications – aplastic anaemia, thrombocytopenia and related complications.
Other complications – Splenic rupture, airway obstruction, myocarditis, hepatitis, and renal failure.

Diagnosis

Typical clinical features
Haematology – increased white cell count, atypical lymphocytes, anaemia, thrombocytopenia.
Heterophile antibody test – e.g. Paul Bunnel test or, monospot test
EBV serology
EBV PCR

Differential diagnosis

Streptococcal sore throat (Group A Streptococcus)
Mononucleosis like syndrome – CMV, HIV seroconversion, Toxoplasma infection, Viral hepatitis, Adenovirus etc.
Leukaemia
Drugs – phenytoin, carbamazepine

Treatment

Usually, self-limiting.
Supporting treatment – nutrition, hydration
Paracetamol, NSAIDs
Steroids and acyclovir – selected cases
Avoid sports for 4 weeks (risk of splenic rupture).

If you are interested to know what is a heterophile antibody see this video.

Heterophile antibody test should not be done in children <4 years or immunocompromised patients (risk of false-negative result)

False-positive results can be seen in – rheumatoid disease, SLE, leukaemia, lymphoma, infections including malaria, HIV, CMV, rubella, viral hepatitis, tularaemia etc.

90% of patients are expected to me positive heterophil antibodies by 3wks, and they disappear at approximately 3 months.

Atypical lymphocytes can also be seen in CMV, HIV, HHV6, rubella, mumps, viral hepatitis, toxoplasmosis, typhus, lead poisoning etc.

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