Infectious mononucleosis (also known as mono, the kissing disease, Pfeiffer's disease, and, in British English, glandular fever) is a disease seen most commonly in adolescents and young adults, characterized by fever, sore throat and fatigue. It is caused by the Epstein-Barr virus (EBV) or the cytomegalovirus (CMV). It is typically transmitted through saliva, usually through kissing or sharing drinks. The virus infects B cells (B-lymphocytes), producing a reactive lymphocytosis and the atypical T cells (T-lymphocytes) which give the disease its name. Symptoms similar to those of mononucleosis can be caused by adenovirus and the protozoan Toxoplasma gondii.

Symptoms and physical signs

The typical symptoms and signs of mononucleosis are:

• fever - this varies from mild to severe, but is seen in nearly all cases.
• enlarged lymph nodes - particularly the posterior cervical lymph nodes, on both sides of the neck.
• sore throat - nearly all patients with EBV-mononucleosis have tonsillitis, usually accompanied by thick exudate.
• fatigue

Some patients may also display:

• enlarged spleen or liver
• aching muscles
• headache
• loss of appetite
• jaundice

The symptoms of infectious mononucleosis usually last 1-2 months, but the virus can remain dormant in the B cells indefinitely after symptoms have disappeared. Many people exposed to the Epstein-Barr virus do not show symptoms of the disease, but carry the virus and can transmit it to others. This is especially true in children, in whom infection seldom causes more than a very mild illness which often goes undiagnosed. This feature, along with mono's long incubation period, makes epidemiological control of the disease impractical. About 6% of people who have had mono will relapse.

Since mononucleosis can cause the spleen to swell, it may in rare cases lead to a ruptured spleen. Rupture may occur without trauma, but impact to the spleen is usually a factor.

Mononucleosis is rarely fatal. Death is usually from severe hepatitis or splenic rupture.

Laboratory tests

The laboratory hallmark of the disease is the presence of so-called atypical lymphocytes (a type of mononuclear cell) on the peripheral blood smear. In addition, the overall white blood cell count is almost invariably increased, particularly the number of lymphocytes.

The mono spot tests for infectious mononucleosis by examining the patient's blood for so-called heterophile antibodies, which cause agglutination of non-human red blood cells. This screening test is non-specific. Confirmation of the exact etiology can be obtained through tests to detect antibodies to the causative viruses. The mono spot test may be negative in the first week, so negative tests are often repeated at a later date.

An older test is the Paul Bunnell test, in which the patient's serum is mixed with sheep red blood cells. If EBV is present, antibodies will usually be present that cause the sheep's blood cells to agglutinate, or stick together. This test has been replaced by the mono spot and more specific EBV and CMV antibody tests.

Treatment

There is no specific treatment for mononucleosis, other than generic remedies to reduce the severity of the symptoms. Aspirin should be avoided, since its use in patients with mononucleosis can cause Reye's syndrome. Acetaminophen must also be used with caution, as it may worsen the hepatitis which often accompanies mononucleosis. Ampicillin and amoxicillin should also be avoided, since they cause an allergic-like rash in 90% of mono patients. This rash may then be incorrectly diagnosed as an allergic reaction to penicillin. In cases accompanied by severe throat pain, corticosteroids may be judiciously prescribed, although some studies have shown that such treatment may increase the risk of the EBV virus causing lymphomas in later years.

External links

• CDC information on EBV (http://www.cdc.gov/ncidod/diseases/ebv.htm)