What is mononucleosis?

Causes and Symptoms

Mononucleosis is caused by the Epstein-Barr virus
, which is transmitted through infected saliva or by blood transfusions. It has an incubation period of four to six weeks. The saliva may remain infective for as long as eighteen months, and after the primary infection, the virus may be present in the nasal secretions and shed periodically for the rest of the host’s life. Many cases occur in adolescents—hence the popular name “the kissing disease.” The virus can be cultured from the throat of 10 to 20 percent of most healthy adults. The incidence of mononucleosis varies seasonally among high school and college students but does not vary among the general population. The disease is fairly common in the United States, Canada, and Europe and occurs in both sexes.

Mononucleosis is characterized by fever, fatigue, anorexia, a sore throat
, chills, a skin rash, bleeding gums, red spots on the tonsils, malaise, and periorbital edema. Lymph nodes in the neck enlarge, and splenomegaly develops in about half of patients. In a small number of patients, liver involvement with mild jaundice occurs.

The diagnosis is made by several different tests, such as the differential white blood count. In mononucleosis, lymphocytes and monocytes make up greater than 50 percent of the blood cells, with a figure of more than 10 percent being atypical. The leukocyte count is normal early in the disease but rises during the second week. Serology studies show an increase in the heterophile antibody titer, although the monospot test is more rapid and can detect the infection earlier and is widely used. Children under four years of age often test negative for heterophil antibodies, but the test will identify 90 percent of cases in older children, adolescents, and adults.

Treatment and Therapy

The treatment of mononucleosis is mainly supportive, since the disease is self-limiting. The patient is usually placed on bed rest during the acute stage of the disease, and activity is limited to prevent rupture of the enlarged spleen, usually for at least two months. Acetaminophen (such as the brand Tylenol) is given for the fever, and saline gargles or lozenges may be used for the sore throat. Patients need to increase their fluid intake. Many doctors use corticosteriods such as prednisone during the course of the disease to lessen the severity of the symptoms. If rupture of the spleen occurs, emergency surgery is necessary to remove the organ.

Complications are uncommon but may include rupture of the spleen, secondary pneumonia, heart involvement, neurologic manifestations such as Guillain-Barré syndrome, meningitis, encephalitis, hemolytic anemia, and orchitis (inflammation of the testes).

Perspective and Prospects

Viruses, such as the one responsible for mononucleosis, were first studied in the 1930s, and they remain a challenge to laboratory investigators. Most information about viruses has come from studying their effects, rather than the viruses themselves. The majority of methods for destroying or controlling viruses are ineffective. There is no prevention for many of the diseases caused by viruses, such as infectious mononucleosis. It may be reassuring to know that the disease seldom causes severe complications if the symptoms are treated and medical care is given to those infected with the Epstein-Barr virus.

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