Mononucleosis

Mononucleosis, also known as mono, is a disease caused by either the Epstein-Barr virus or the cytomegalovirus. Usually, it is spread though saliva and mucus, but it can be transmitted in other ways. Symptoms of mononucleosis can include fever, swollen lymph nodes, extreme exhaustion, sore throat, and other symptoms. The symptoms usually get better in one or two months without any treatment, and most people can return to work or school after three to four weeks.

 

What Is Mononucleosis?

Mononucleosis (mono) is an illness caused by a virus, which can result in fever, swollen lymph glands, and a sore throat.
 

How Common Is Mononucleosis?

Mononucleosis is most common in people 10 to 35 years old, with its peak incidence in those 15 to 17 years old. Only 50 people out of 100,000 in the general population get mononucleosis, but it strikes as many as 2 out of 1,000 people in their teens and twenties, especially those in high school, college, and the military.
 

What Causes It?

Two viruses can cause mononucleosis: the Epstein-Barr virus (EBV) and cytomegalovirus (CMV). Both viruses are in the herpes family, whose other members include viruses responsible for cold sores and chickenpox. EBV causes mononucleosis in 85 percent of cases. When EBV is the cause, it is also referred to as infectious mononucleosis. When CMV causes it, it is also referred to as mononucleosis syndrome, or CMV mononucleosis.
 
(Click Mononucleosis Causes for more information on this topic.)
 

Understanding the Epstein-Barr Virus

The Epstein-Barr virus, frequently referred to as EBV, is a member of the herpesvirus family and is one of the most common human viruses. The virus occurs worldwide, and most people become infected with EBV sometime during their lives. In the United States, as many as 95 percent of adults between 35 and 40 years of age have been infected. Infants become susceptible to EBV as soon as maternal antibody protection (immunity present at birth) disappears.
 
Many children become infected with EBV, and these infections usually cause no symptoms, or are indistinguishable from the other mild, brief illnesses of childhood. In the United States, and in other developed countries, many people are not infected with EBV during their childhood years. When EBV infection occurs during adolescence or young adulthood, it causes infectious mononucleosis 35 to 50 percent of the time.
 

How Is It Spread?

The illness is usually spread though saliva and mucus, which is where the "kissing disease" nickname comes from. In addition, mononucleosis can be transmitted in other ways, such as sipping from the same straw or glass as an infected person, or even being close when the person coughs or sneezes.
 
(Click How Is Mono Spread? for more information.)
 

Incubation Period

When a person becomes infected with the virus that causes mononucleosis, the virus begins to multiply within the body. After four to eight weeks, mono symptoms can begin. The period between becoming infected and the start of symptoms is called the mononucleosis incubation period.
 

Symptoms of Mononucleosis

Symptoms will vary among individuals. Some people experience mild symptoms of mono, while others can have very serious mono symptoms.
 
Perhaps the most distinguishing symptom of mononucleosis is enlarged glands or lymph nodes, especially in the neck, but also in the armpit and groin.
 
Another common mononucleosis symptom is fever. A temperature as high as 103ºF (39.5ºC) is not uncommon.
 
Other symptoms can include:
 
  • Lack of energy
  • Body aches
  • Chills
  • Loss of appetite
  • Sore throat
  • Tonsillitis
  • White patches on the back of the throat
  • Swollen spleen
  • Swelling around the eye
  • Mild liver tenderness
  • Rash.

 

(Click Mononucleosis Pictures to see what some of these symptoms look like.)

 

Making a Diagnosis

In order to make a mononucleosis diagnosis, the doctor will usually ask a number of questions and perform a physical exam. Because mono symptoms can be very similar to other illnesses, doctors often recommend tests to find out exactly what the problem is. One of these tests is the monospot blood test.
 
(Click Mononucleosis Diagnosis for a more in-depth look at this topic.)
 

Treatment

There is currently no treatment to kill either of the viruses that cause the illness; therefore, treatment for mononucleosis is focused on providing relief of mono symptoms as the body fights the virus.
 

Prognosis

Mononucleosis symptoms usually get better in one or two months without any treatment. Most people can return to work or school after three to four weeks. Others may be exhausted and unable to return to their full activities for months.
 
It is also possible that complications can occur. Although these complications occur infrequently, when they do occur, they can be dramatic.
 
Complications of mononucleosis can affect the:
 
  • Blood
  • Spleen
  • Nervous system
  • Liver
  • Heart
  • Lungs.
     
Mononucleosis is rarely fatal.
 
(Click Mononucleosis Prognosis or Complications of Mono for more information.)
 

Other Names for Mononucleosis

Other names that people use for the condition include:
 
  • Infectious mononucleosis
  • Mononucleosis syndrome
  • Kissing disease
  • Mono
  • Glandular fever.

 

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Written by/reviewed by: Arthur Schoenstadt, MD
Last reviewed by: Arthur Schoenstadt, MD