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Mononucleosis, or mono, is a viral infection that causes fever, sore throat, and swollen lymph glands, most often in the neck.


Mono is often spread by saliva and close contact. It is known as "the kissing disease." Mono occurs most often in people ages 15 to 17, but the infection may develop at any age.

Mono is usually linked to the Epstein-Barr virus (EBV). Rarely, it is caused by other viruses, such as cytomegalovirus (CMV).


Mono may begin slowly with fatigue, a general ill feeling, headache, and sore throat. The sore throat slowly gets worse. Your tonsils become swollen and develop a whitish-yellow covering. Often, the lymph nodes in the neck are swollen and painful.

A pink, measles-like rash can occur, and is more likely if you take the medicine ampicillin or amoxicillin for a throat infection. (Antibiotics should NOT be given without a test that shows you have a strep infection.)

Common symptoms of mono include:

Less common symptoms are:

Exams and Tests

Your health care provider will examine you. They may find:

  • Swollen lymph nodes in the front and back of your neck
  • Swollen tonsils with a whitish-yellow covering
  • Swollen liver or spleen
  • Skin rash

Blood tests will be done, including:

  • White blood cell (WBC) count: will be higher than normal if you have mono
  • Monospot test: will be positive for infectious mononucleosis
  • Antibody titer: tells the difference between a current and past infection


The goal of treatment is to relieve symptoms. Steroid medicine (prednisone) may be given if your symptoms are severe.

Antiviral drugs, such as acyclovir, have little or no benefit.

To relieve typical symptoms:

  • Drink plenty of fluids.
  • Gargle with warm salt water to ease a sore throat.
  • Get plenty of rest.
  • Take acetaminophen or ibuprofen for pain and fever.

Also avoid contact sports if your spleen is swollen (to prevent it from rupturing).

Outlook (Prognosis)

The fever usually drops in 10 days, and swollen lymph glands and spleen heal in 4 weeks. Tiredness usually goes away within a few weeks, but it may linger for 2 to 3 months.

Possible Complications

Complications of mononucleosis may include:

  • Anemia, which occurs when red blood cells in the blood die sooner than normal
  • Hepatitis with jaundice (more common in people older than 35)
  • Swollen or inflamed testicles
  • Nervous system problems (rare), such as Guillain-Barré syndrome, meningitis, seizures, damage to the nerve that controls movement of the muscles in the face (Bell's palsy), and uncoordinated movements
  • Spleen rupture (rare, avoid pressure on the spleen)
  • Skin rash (uncommon)

Death is possible in people who have a weakened immune system.

When to Contact a Medical Professional

The early symptoms of mono feel very much like any other illness caused by a virus. You do not need to contact a provider unless your symptoms last longer than 10 days or you develop:

  • Abdominal pain
  • Breathing difficulty
  • Persistent high fevers (more than 101.5°F or 38.6°C)
  • Severe headache
  • Severe sore throat or swollen tonsils
  • Weakness in your arms or legs
  • Yellow color in your eyes or skin

Call 911 or go to an emergency room if you develop:

  • Sharp, sudden, severe abdominal pain
  • Stiff neck or severe weakness
  • Trouble swallowing or breathing


People with mono may be contagious while they have symptoms and for up to a few months afterwards. How long someone with the disease is contagious varies. The virus can live for several hours outside the body. Avoid kissing or sharing utensils if you or someone close to you has mono.

Alternative Names

Mono; Kissing disease; Glandular fever


Bope ET, Kellerman RD. Symptomatic care pending diagnosis. In: Bope ET, Kellerman RD, eds. Conn's Current Therapy 2016. Philadelphia, PA: Elsevier; 2016:chap 1.

Jenson HB. Epstein-Barr virus. In: Kliegman RM, Stanton BF, St Geme JW, Schor NF, eds. Nelson Textbook of Pediatrics. 20th ed. Philadelphia, PA: Elsevier; 2015:chap 254.

Johannsen EC, Kaye KM. Epstein-Barr virus (infectious mononucleosis, Epstein-Barr virus-associated malignant diseases, and other diseases). In: Mandell GL, Bennett JE, Dolin R, eds. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases. 8th ed. Philadelphia, PA: Elsevier Saunders; 2014:chap 141.

Schooley RT. Epstein-Barr virus infection. In: Goldman L, Schafer AI, eds. Goldman's Cecil Medicine. 25th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 377.

Review Date 2/15/2016

Updated by: Neil K. Kaneshiro, MD, MHA, Clinical Assistant Professor of Pediatrics, University of Washington School of Medicine, Seattle, WA. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.

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