Infectious mononucleosis (Mono) is often referred to as the “kissing disease” due to it's manner of spreading from one individual to another. Actually, Mono is caused by a type of Epstein-Barr virus (EBV), a virus that is thought to be responsible for other conditions such as Chronic Fatigue Syndrome. EBV occurs in two forms that are widely prevalent in nature and are not distinguished by conventional tests.

EBV is transmitted by salivary secretions, usually from an asymptomatic person shedding the virus. Transmission often occurs from adults to infants or among young adults by transfer of saliva during kissing. The virus infects the cells of the oropharynx and salivary glands and is shed from these cells. Infectious mononucleosis is characterized by fever, sore throat, and swollen or infected lymph glands. EBV is also associated with several human tumors, including nasopharyngeal carcinoma, Burkitt's lymphoma, Hodgkin's disease, and in patients with immunodeficiencies (including AIDS), B-cell lymphoma.(1) The virus was originally discovered in association with Burkitt's lymphoma cells, and is a member of the family Herpesviridae.

Epstein-Barr virus infections occur worldwide. In fact, by adulthood, over 90 percent of individuals have been infected and have antibodies to the virus. Infections occur with greatest frequency in early childhood, with another peak during late adolescence. In areas with lower standards of hygiene, such as those observed in lower socioeconomic classes and developing nations, the infection is seen mostly in young childhood, while in areas of higher standards of hygiene, the infection occurs primarily in young adulthood. Most EBV infections in infants and young children are either asymptomatic, or present as a mild pharyngitis with or without tonsillitis. In contrast, when seen in late adolescence, it very frequently presents as infectious mononucleosis.

With mononucleosis, there is a lengthy incubation period of around 30 to 50 days. After that there is a period of three to five days when the individual experiences symptoms such as sore throat, fever, and asthenia. When the individual is examined, the examining physician will check all of the presenting symptoms and determine if a test for mononucleosis is warranted. The physician will also want to check the size of the spleen and liver to make sure they are not enlarged. Problems with the liver are sometimes found in cases of mononucleosis.(2)

In some cases, the fatigue, myalgia, and malaise may be present for one to two weeks prior to onset of fever, sore throat, and swollen glands. Most patients have symptoms for two to four weeks, but malaise and difficulty concentrating can persist for months. Complications from mononucleosis are uncommon and in most cases, the condition is self-limiting.