Mono, a.k.a. Mononucleosis or the Kissing Disease

A Reason to Kiss and Tell

Mononucleosis, or “mono”, is a common infection among young adults and teenagers. This viral infection is spread through saliva, hence the nickname, the “kissing disease”.

Type of Microbe: Epstein-Barr virus (or EBV), belonging to the family of herpes viruses

How it spreads: The virus is spread primarily through the saliva and is not normally spread through the air or blood. There have been some links to sexual transmission, as well.

Who’s at risk? The highest rates of mono are in teenagers who haven't been exposed already in childhood, between the ages of 10 and 19 years. In children younger than 10 years, the risk is lower, but mild infections may be under-diagnosed. Mono is most common in places where there are a lot of young adults, such as in the military and in colleges. Because the virus is so common, most people get infected by the time they reach adulthood. In fact, up to 95% of adults (ages 35 to 40) have been infected at some time in their lives.

Symptoms: Fever, sore throat, fatigue, and swollen lymph nodes are common symptoms in teenagers. In younger children, these symptoms are either absent or very mild. Older adults are less likely to get infectious mononucleosis (since 95% of adults were already exposed) but when they the infection they are more likely to have more severe presentations, including enlarged livers and jaundice -- possibly requiring hospitalization, but not as likely to have sore throats or swollen lymph nodes .

People who have been infected don’t show symptoms for 4 to 8 weeks after being exposed. Rash can also be seen usually in the setting of antibiotics.

Diagnosis: Diagnosis is based on a combination of symptoms and the age of the patient. For confirmation of EBV infection, your doctor will want to run a blood test that measures white blood cells, the heterophile antibody test, and possibly EBV antibodies.

Individuals who have mono will have an increased number of atypical (unusual) white blood cells and antibodies that recognize Epstein-Barr viral proteins. Heterophile antibodies in the setting of a compatible clinical syndrome make the diagnosis of infectious mononucleosis. EBV antibodies are useful in making the diagnosis in cases of infectious mononucleosis where heterophile antibody is negative.

Prognosis: The acute symptoms resolve in about 2 weeks. More lingering symptoms, including fatigue and low energy, may last up to 4 months, but the prognosis is generally good for most people. There are a few potential complications, but most are rare (see “complications” below).

Treatment: Treatment is geared to symptom reduction. Acetaminophen (Tylenol) is given for fever, throat lozenges are given for ​a sore throat, and drinking lots of fluids is recommended. Unfortunately, studies have not revealed a benefit to treating with antivirals and steroid medications are only used when there is concern for closure of the airway.

Athletes should talk to their doctor about how long to refrain from contact sports to prevent rupturing of the spleen.

Prevention: Because many healthy people carry the virus in their saliva without showing any symptoms, it is almost impossible to prevent spread of the disease.

How it causes disease: The virus passes through the saliva into the superficial epithelial cells of the mouth and throat where it makes copies and goes on to infect white blood cells called B cells. Viral infection of B cells results in dissemination of the virus throughout the lymph, glandular and splenic system (known as the lymphoreticular system).

Complications: Rarely throat obstruction, swollen spleen or liver, jaundice, and splenic rupture can occur in patients with mono, but these complications are rare. Long lasting mono (>6 months), or “chronic EBV infection”, is rare and sometimes may be diagnosed as chronic fatigue syndrome. Though not necessarily associated with infectious mononucleosis, certain cancers are associated with EBV. The Epstein-Barr Virus is associated with Burkitt’s lymphoma, nasopharyngeal carcinoma, Hodgkins and primary CNS lymphoma. EBV is not the sole cause of such cancers, but but it is associated.


Epstein-Barr Virus and Infectious Mononucleosis. National Center for Infectious Diseases. Centers for Disease Control and Prevention. November 6, 2008.

Epstein-Barr Virus. MedlinePlus. US National Library of Medicine and the National Institutes of Health.

Ebell MH. Epstein-Barr Virus Infectious Mononucleosis. American Family Physician (2004) 70:1279.

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