Mono, which is more formally referred to as mononucleosis, is an infectious disease caused by exposure to the Epstein-Barr virus, or EBV.

In the United States, approximately 95 percent of people between the ages of 35 and 40 carry an inactive form of this infection, according to the Centers for Disease Control and Prevention. Though many patients never develop mono symptoms, symptomatic cases of this infection typically resolve within 1 to 2 months of onset. Patients who continue to experience mono symptoms for longer than 6 months may be diagnosed with chronic mono.

Most people, who have infectious mononucleosis, or mono, get it only once. Rarely, however, mononucleosis symptoms may recur months or even years later.

Most cases of mononucleosis are caused by infection with the Epstein-Barr virus (EBV). Once you’re infected with EBV, you carry the virus — usually in a dormant state — for the rest of your life. Periodically, however, the virus may reactivate. When this happens, the virus can be detected in your saliva — but you’re not likely to become ill. Rarely, reactivated EBV may cause illness in people who have weak immune systems, such as those who have AIDS.

Mononucleosis sometimes leads to a serious condition called chronic active EBV infection, which is characterized by persistent illness more than six months after the initial mononucleosis diagnosis.

Typically resolve within 1 to 2 months of onset. Patients who continue to experience mono symptoms for longer than 6 months may be diagnosed with chronic mono.

Swollen Lymph Nodes

One of the characteristic symptoms of chronic mono is swelling of the lymph nodes, report Dr. Gotoh and colleagues in a May 15, 2008 article published in the journal “Clinical Infectious Diseases.” The lymph nodes are a part of the endocrine system and work with the immune system to remove infectious pathogens from the bloodstream. Patients with this infection can accumulate white blood cells, a type of immune cell, within the lymph nodes, which leads to swelling. Enlarged lymph nodes can appear within the neck, groin or underneath the armpits and may be painless or slightly tender to the touch. In patients with chronic mono, these symptoms can persist for several months or years.

Fever

Patients with chronic mono can experience persistent or recurrent fever as a symptom of this condition, explain CDC health officials. Fever symptoms can contribute to the appearance of additional symptoms, including headache, chills, sweating or body aches. Certain patients may also experience night sweats in conjunction with fever symptoms, reports MayoClinic.com. Patients who develop chronic fever symptoms should speak with a doctor immediately as fever can also be a sign of alternate medical problems.

Sore Throat

Long-lasting sore throat symptoms can occur in certain patients due to chronic mono, explains the CDC. Patients can develop sore, swollen tonsils and can have difficulty swallowing due to sensations of pain and discomfort. Sore throat symptoms can persist for several months and may accompany recurrent strep throat infections that do not respond to antibiotic treatment, reports MayoClinic.com. These chronic mono symptoms can limit a patient’s appetite and may contribute to unintended weight loss in certain patients.

Fatigue

Chronic mono can cause severe fatigue symptoms in patients. Affected patients may sleep for longer periods of time throughout the day or may have difficulty functioning normally while at work or school. Patients who exhibit excessive fatigue symptoms for more than 6 months should be evaluated by a doctor for other illnesses, such as chronic fatigue syndrome, advises the CDC.