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 caused by 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 are typically not given without a test that shows you have a strep infection.)
Common symptoms of mono include:
- General discomfort, uneasiness, or ill feeling
- Loss of appetite
- Muscle aches or stiffness
- Sore throat
- Swollen lymph nodes, most often in the neck and armpit
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:
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).
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. Nearly everyone recovers completely.
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 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 the local emergency number 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.
Mono; Kissing disease; Glandular fever
- Mononucleosis - photomicrograph of cells
- Mononucleosis - photomicrograph of cells
- Infectious mononucleosis #3
- Infectious mononucleosis
- Mononucleosis - photomicrograph of cell
- Gianotti-Crosti syndrome on the leg
- Mononucleosis - view of the throat
- Mononucleosis - mouth
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Review Date 3/10/2022
Updated by: Jatin M. Vyas, MD, PhD, Associate Professor in Medicine, Harvard Medical School; Associate in Medicine, Division of Infectious Disease, Department of Medicine, Massachusetts General Hospital, Boston, MA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.