What is Mononucleosis? What is it's cause?

Infectious Mononucleosis (Mono)

Infectious mononucleosis, "mono," or "kissing disease," is a contagious illness caused by the Epstein-Barr virus (EBV). EBV is a member of the herpes virus family.  The infection can be spread by saliva and hence the term “kissing disease”. A person with mono can also pass the disease by coughing or sneezing, causing small droplets of infected saliva and/or mucus to be suspended in the air, which can be inhaled by others. Mono commonly occurs in adolescents and young adults. The designation "mononucleosis" refers to an increase in a special type of white blood cells (lymphocytes) in the bloodstream relative to the other blood components.

Causes of mono

By the time most people reach adulthood, an antibody against EBV can be detected in their blood. This means that most people, sometime in their lives, have been infected with EBV. The body's immune system produces antibodies to attack and help destroy invading viruses and bacteria.
Once infected, a person develops lifelong immunity to future infections from the disease. It is important to note that people who have had mono can continue to shed virus particles in their saliva during reactivations of the viral infection throughout their lifetime.

Risk factors

The EBV can infect any person. Mono is most often diagnosed in adolescents and young adults aged 10-24. The virus can be spread by intimate contact with a person who has mono or by sharing drinking glasses, eating utensils, dishes, or a toothbrush with an infected person. A person does not have to have symptoms of mono to spread EBV.

Symptoms of mono?

Sometimes no symptoms are present; however, initial symptoms of mono may be a general lack of energy (fatigue), a loss of appetite, and chills. These initial symptoms can last from one to three days before the more intense symptoms of the illness begin.

Common intense symptoms include:

  • Severe sore throat
  • Fever (101° to 104° F)
  • Swollen glands all over the body especially the lymph nodes in the neck area. It is typically the severe sore throat with white patches on the tonsils (may look like strep throat) that prompt people to contact their doctor.
  • Swollen tonsils
  • Headache
  • Body aches
  • Splotchy red rash over the entire body
  • Pain in the upper left part of the abdomen indicating the spleen has become enlarged

How is mono diagnosed?

The diagnosis of mono is suspected by the doctor based on the above signs and symptoms. Mono is confirmed by blood tests as well as other tests to exclude other possible causes of the symptoms, such as Strep throat. Early in the course of mono, blood tests may show an increase in one type of white blood cell (lymphocyte). Some of these increased lymphocytes have an unusual or "atypical" appearance when viewed under a microscope, which suggests mono.

Treatment of mono?

In most cases there is no specific treatment. The illness is usually self-limited and resolves on its own. Treatment is directed toward the relief of symptoms. Available antiviral drugs have no significant effect on the overall outcome of mono and may actually prolong the course of the illness. Vitamin C is highly recommended. In addition, sufficient amount of sleep and rest is important. It is recommended that patients with mono avoid participation in any contact sports during the first six to eight weeks following the onset to prevent trauma to the enlarged spleen.

What are the complications of mono?

  • Enlarged Spleen - An enlarged spleen can cause serious health problems. A blow to an enlarged spleen could cause it to rupture. Symptoms of rupture include a sudden, sharp pain in the left side of the upper abdomen. If such pain occurs, seek medical attention immediately — you may need surgery. To reduce this risk, avoid heavy lifting and contact sports for 6 to 8 weeks after you become ill with mono or until your doctor says it is safe. In very rare cases, the spleen may rupture on its own.


  • Jaundice – Jaundice is a yellowing of the skin and the whites of your eyes (jaundice). This occurs occasionally, usually in people older than 35.

Less common complications

  • Anemia — a decrease in red blood cells and in hemoglobin, an iron-rich protein in red blood cells
  • Thrombocytopenia — low count of platelets, which are blood cells involved in clotting
  • Pericarditis – Inflammation of the heart sac surrounding the heart
  • Myocarditis — Inflammation of the heart
  • Complications involving the nervous system (meningitis, encephalitis, Guillain-Barre syndrome)
  • Encephalitis—inflammation of the brain
  • Swollen tonsils – leading to obstructed breathing

*The Epstein-Barr virus can cause much more serious illness in people who have impaired immune systems, such as people with HIV/AIDS or people taking drugs to suppress immunity after an organ transplant.