Infectious mononucleosis — Rapid

Synopsis

Recognise Epstein–Barr virus infectious mononucleosis, protect the airway and spleen, distinguish alternative causes of glandular-fever illness and avoid unnecessary antibiotics and unsafe activity.

The typical syndrome combines fever, pharyngitis, posterior cervical lymphadenopathy and fatigue, but age and immune status alter presentation.
Examine the airway, hydration, liver and spleen and ask about abdominal pain; tonsillar appearance alone cannot determine severity.
A heterophile antibody test may be negative early or in younger people. EBV-specific serology clarifies timing when the diagnosis matters and the initial test is non-diagnostic.
Avoid amoxicillin or ampicillin for uncomplicated suspected EBV because they do not treat the virus and commonly provoke a widespread rash.
Treatment is usually rest, fluids and appropriate analgesia. Corticosteroids are not routine and are reserved for selected severe complications with specialist input.
Advise no contact or collision sport, heavy lifting or other trauma-risk activity for at least the first month after symptom onset and until clinically recovered; use individual specialist review for ongoing splenomegaly or high-risk return.
Consider acute HIV, cytomegalovirus, streptococcal tonsillitis, toxoplasmosis, haematological malignancy and diphtheria where epidemiology or features do not fit.

Key red flags

Threatened airway

Progressive tonsillar swelling, muffled voice, drooling, stridor, inability to swallow or respiratory effort requires urgent airway-capable assessment.

Splenic complication

Left upper-quadrant or shoulder-tip pain, dizziness, hypotension or collapse during acute illness suggests splenic injury or rupture.

Investigation priorities

Full blood count and blood filmFirst step

Identify lymphocytosis, atypical lymphocytes, cytopenia and an alternative haematological pattern.

Management branches

Uncomplicated syndromeSupport recovery and protect the spleen

The patient is stable, drinking and has no airway, hepatic, haematological or abdominal emergency.

Confirm the clinical pattern, use selective FBC and EBV testing when helpful and avoid antibiotics unless bacterial infection is established.
Provide fluids, appropriate analgesia, rest and written advice about fatigue, alcohol while liver tests are abnormal and transmission through saliva.
Advise no collision sport, heavy lifting or other trauma-risk activity for at least the first month after symptom onset and until clinically recovered, with individual review before high-risk return.

Airway or severe complicationEscalate beyond routine supportive care

There is stridor, inability to swallow, severe cytopenia, neurological disease, hepatic failure or suspected splenic rupture.

Perform ABCDE, involve ENT, anaesthetic, surgical, haematology or liver teams according to the complication and obtain urgent blood tests and imaging without destabilising the airway.
Use corticosteroids only for a selected severe indication through specialist care; treat bacterial coinfection or haemodynamic compromise on its own evidence.
Monitor closely until airway, hydration, blood counts, liver function or abdominal findings have demonstrably stabilised.

Key medicines

ParacetamolFor most adults give 500 mg to 1 g by mouth at intervals of at least four hours, no more than 4 g daily.Reduce maximum exposure in low weight, liver dysfunction, malnutrition or heavy alcohol use, and check combination remedies to avoid overdose.

Corticosteroid for selected severe complicationUse a short specialist-directed systemic regimen only for threatened airway or another accepted severe immune complication.Not routine for fatigue or uncomplicated pharyngitis; exclude bacterial deep-neck infection, monitor glucose and secondary infection, and document the precise indication and stop plan.

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