Mononucleosis, or mono, is a viral infection that causes fever, sore throat, and swollen lymph glands, most often in the neck.
Mono; Kissing disease; Glandular fever
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.)
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 health care provider unless your symptoms last longer than 10 days or you develop:
Persistent high fevers (more than 101.5°F)
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.
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Jatin M. Vyas, MD, PhD, Assistant Professor in Medicine, Harvard Medical School; Assistant in Medicine, Division of Infectious Disease, Department of Medicine, Massachusetts General Hospital, Boston, MA. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.