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What is infectious mononucleosis ("mono")?

Infectious mononucleosis, "mono," "kissing disease," and glandular fever are all terms popularly used for the very common illness caused by the Epstein-Barr virus (EBV). This common viral infection causes fever, sore throat, and enlarged lymph nodes. The illness generally goes away without medical help. However, it may last from weeks to months. Treatment is mainly to ease symptoms, usually at home, with plenty of rest and fluids.

What is the Epstein-Barr virus?

EBV is a member of the herpesvirus family and causes more than 90% of cases of mononucleosis. EBV is a double-stranded DNA virus named for the English virologists professor Sir Anthony Epstein and Yvonne M. Barr. 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 as a result of the EBV infection.

What is the cause of mono?

The EBV that causes mono is found throughout the world. By the time most people reach adulthood, an antibody against EBV can be detected in their blood. In the U.S., up to 95% of adults 35-40 years of age have antibodies directed against EBV. This means that most people, sometime in their lives, have been infected with EBV. While there are other illnesses falling under the broad classification of mononucleosis that cause similar symptoms and an increase in blood lymphocytes, the form caused by the EBV is by far the most common.

What are the risk factors for mono?

The EBV can infect anyone. By adulthood, 90%-95% of men and women have been infected with EBV; infections most often occur in people 5-25 years of age. Not surprisingly, 1%-3% of college students contract mono each year, as it is most often transmitted via saliva (hence the name “kissing disease”). However, mono can also be spread through blood and genital secretions.

How is mono spread?

Mono is usually spread by person-to-person contact. Saliva is the primary method of transmitting mono. Infectious mononucleosis developed its common name of "kissing disease" from this prevalent form of transmission among teenagers. A person with mono can also pass on the disease by coughing or sneezing, causing small droplets of infected saliva and/or mucus to be suspended in the air and inhaled by others. Sharing food or beverages from the same container or utensil can also transfer the virus from one person to another, since contact with infected saliva may result.

How long is mono contagious?

Most people have been exposed to the virus as children, and as a result of the exposure, they have developed immunity to the virus. It is of note that most people who are exposed to the EBV don't ever develop mononucleosis. The incubation period for mono, meaning the time from the initial viral infection until the appearance of symptoms, is between four and six weeks. During an infection, a person is likely able to transmit the virus to others for at least a few weeks.

Reactivations of mono

Research has shown that, depending on the method used to detect the virus, anywhere from 20% to 80% of people who have had mononucleosis and have recovered will continue to secrete the EBV in their saliva for years due to periodic "reactivations" of the viral infection. Since healthy people without symptoms also secrete the virus during reactivation episodes throughout their lifetime, isolation of people infected with EBV is not necessary. It is currently believed that these healthy people, who nevertheless secrete EBV particles, are the primary reservoir for transmission of EBV among humans.

What are the symptoms of mono?

The initial symptoms of mono are a general lack of energy (malaise), loss of appetite, and chills. These initial symptoms can last from one to three days before the more intense symptoms of the illness begin. The more common intense symptoms include a severe sore throat, fever, and swollen glands (lymph nodes) in the neck area. It is typically the severe sore throat that prompts people to contact their doctor.

What are the signs of mono?

In addition to a fever from 102 F-104 F, the most common signs of mono are a very reddened throat and tonsils and swollen lymph glands (nodes) in the neck. The tonsils have a whitish coating in at least one-third of the cases. The spleen (sometimes referred to as the body's biggest lymph node), an organ found in the left upper abdomen underneath the rib cage, becomes enlarged or swollen in about 50% of patients with mono. An enlarged liver may also occur. About 5% of patients have a splotchy red rash over the body, which has a similar appearance to the rash of measles.

How is mono diagnosed?

A diagnosis of mono is suspected by the doctor based on the patient's symptoms and signs. Mono is confirmed by blood tests that may also include tests to exclude other possible causes of the symptoms, such as tests to rule out 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.

More specific blood tests, such as the monospot and heterophile antibody tests, can confirm the diagnosis of mono. These tests rely on the body's immune system to make measurable antibodies against the EBV. Unfortunately, the antibodies may not become detectable until the second or third week of the illness. A blood chemistry test may reveal abnormalities in liver function.

What is the usual course and treatment of mono?

In most cases of mono, no specific treatment is necessary. The illness is usually self-limited and resolves in much the same way as other common viral illnesses. 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. For the most part, supportive or comfort measures are all that is necessary. Acetaminophen can be given for fever and any body- or headaches. A sufficient amount of sleep and rest is important. The throat soreness is worst during the first five to seven days of illness and then subsides over the next seven to 10 days.

Are there any long-term effects of mono?

A feeling of fatigue or tiredness may persist for months following the acute phase of the illness. 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. Patients can continue to have virus particles present in their saliva for as long as 18 months after the initial infection. When symptoms persist for more than six months, the condition is frequently called "chronic" EBV infection.

What are the complications of mono?

A common, but usually not serious, complication of mono is a mild inflammation of the liver or hepatitis. This form of hepatitis is rarely serious and rarely requires treatment. The enlargement of the spleen that occurs with mono makes traumatic rupture of the spleen a possible complication. Fortunately, the more severe complications of mono are quite rare, and mono is very rarely fatal in healthy people. The rare severe complications include destruction of red blood cells (hemolytic anemia) and inflammation of the sac surrounding the heart (pericarditis), the heart muscle itself (myocarditis), and the brain (encephalitis). Mono tends to be more aggressive in patients with abnormal immune systems, such as people with AIDS or those who are taking medications that suppress immune function. The EBV has been associated with some types of cancers, most commonly lymphomas. As well, some studies have linked EBV to the development of at least one subtype of Hodgkin's disease.

Infectious Mononucleosis At A Glance

  • Infectious mononucleosis is a contagious illness caused by the Epstein-Barr virus (EBV).
  • The infection can be spread by saliva, and the incubation period for mono is four to six weeks.
  • Most adults have laboratory evidence (antibodies against the EBV) indicative of a previous infection with EBV and are immune to further infection.
  • Symptoms include fever, fatigue, sore throat, and swollen lymph nodes.
  • Diagnosis is confirmed by blood tests.
  • Mono can cause liver inflammation (hepatitis) and enlargement of the spleen.
  • People who have had mono can continue to shed virus particles in their saliva during reactivations of the viral infection throughout their lifetime.
  • Vigorous contact sports should be avoided in the illness and recovery phase to prevent rupture of the spleen.

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