Infectious mononucleosis (glandular fever)
A common viral infection, usually from the Epstein-Barr virus, causing a prolonged sore throat, fever, swollen glands and marked fatigue — especially in teenagers and young adults. It resolves on its own, but the tiredness can linger for weeks.
What it is
Infectious mononucleosis, or glandular fever, is caused in most cases by the Epstein-Barr virus (EBV), spread through saliva (hence 'the kissing disease'). It is especially common in adolescents and young adults. After an incubation of several weeks it causes a triad of a severe, prolonged sore throat, fever, and widely swollen lymph glands, usually with pronounced fatigue that can outlast the other symptoms by weeks. The spleen often enlarges, and the liver can be mildly inflamed. The blood count characteristically shows a rise in lymphocytes, including large 'atypical' ones, and mild elevations of the liver enzymes are common. It is self-limiting and treated supportively. Two practical points matter: antibiotics are unhelpful (and amoxicillin can cause a rash in mono), and because the spleen is enlarged and can rarely rupture, contact and collision sports are avoided for several weeks.
Key lab markers
- Lymphocytes — raised, with characteristic large 'atypical' lymphocytes on the blood film.
- Full blood count (WBC) — often raised due to the lymphocytes.
- Monospot / heterophile antibody test — a rapid screen (can be falsely negative early).
- EBV-specific antibodies — confirm the diagnosis when needed.
- Liver enzymes (ALT, AST) — often mildly raised from mild hepatitis.
- Throat swab — sometimes to exclude bacterial (strep) tonsillitis.
Symptoms
- A severe, prolonged sore throat with enlarged tonsils
- Fever
- Widely swollen, tender lymph glands, especially in the neck
- Marked fatigue and malaise, often lingering for weeks
- Headache, body aches
- An enlarged spleen (upper-left abdominal fullness)
- Sometimes a mild rash, or jaundice from liver involvement
Related symptoms
Related lab panels
When to discuss with a doctor
Glandular fever is diagnosed clinically and with a blood count and antibody test, and it is managed supportively — rest, fluids and simple pain relief — as it resolves on its own, though fatigue can persist for weeks. See a doctor to confirm the diagnosis and exclude bacterial tonsillitis. Seek urgent care for difficulty breathing or swallowing due to very swollen tonsils, or for sudden severe left-upper abdominal or shoulder-tip pain, which could indicate the rare complication of a ruptured spleen. Because of the enlarged spleen, contact and collision sports should be avoided for several weeks as advised. Mediora.AI can flag the raised-lymphocyte and mildly-raised-liver-enzyme pattern typical of mono; the diagnosis belongs with your doctor.