Infectious mononucleosis, colloquially referred to as “mono,” is a benign infection characterized by fever, swollen lymph nodes and fatigue that may continue for weeks or months. It is also known as “the kissing disease” since it’s primarily transmitted through saliva, according to the National Institutes of Health. It can also spread through shared utensils and aerosol droplets from coughing and sneezing. The infection is most common in people between the ages of 10 to 30.

Infectious mononucleosis is usually caused by the Epstein-Barr virus, which infects the majority of the human population and establishes lifelong persistence in immune cells. However, only 35 to 50 percent of people infected with the virus will develop infectious mononucleosis, according to the Centers for Disease Control and Prevention.

Symptoms

The three classical symptoms of infectious mononucleosis are fever, sore throat, and swollen lymph glands, according to the CDC. Although it could further develop into swollen spleen, hepatitis, jaundice and, rarely, inflammation of the heart (myocarditis), infectious mononucleosis is almost never fatal.

Fatigue is a common complaint among mononucleosis patients. A 2006 British study examined the medical records of 1,438 patients and found that they are four times more likely to feel fatigued after infectious mononucleosis and the feeling usually lasts about eight weeks for most patients. Chronic fatigue, however, is a far less common side effect, with only 2 percent of the patients in the study still diagnosed with fatigue a year later.

Diagnosis & Tests

A patient’s medical history, in addition to a white blood cell count or antibody tests, should be able to confirm diagnosis, according to the NIH. A rapid test for strep throat may be performed since streptococcal infection occasionally accompanies the sore throat of infectious mononucleosis.

Though physicians may try to feel for signs of an enlarged spleen during physical examinations, the practice is only 27 to 58 percent accurate at detecting a truly enlarged spleen, according to a 2004 article in the journal American Family Physician. Therefore, the inability to feel an enlarged spleen should not be used to dismiss the likelihood of infectious mononucleosis.

Complications

Although spontaneous splenic rupture is a rare complication and it’s estimated to occur in 0.1 to 0.5 percent of mononucleosis cases, it is still a serious concern, according to a 2007 article in the journal Pediatrics. The spleen is vulnerable to ruptures within the first three to four weeks of symptoms, independent of spleen size, according to a 2008article written for the American Medical Society for Sports Medicine. Therefore, athletes should resume only light, non-contact activities after three weeks of symptoms, and delay contact sports for as long as seven weeks or more, depending on the type of sports. Activities associated with abdominal exertion, such as rowing or weightlifting, should merit extra considerations, according to the article.

Some studies suggested that acute infectious mononucleosis and Epstein-Barr virus may permanently alter or impair the immune response. A 2007 Danish study looked at the possible correlation between multiple sclerosis and infectious mononucleosis and found there’s a two-fold increase in multiple sclerosis risk for those who had been infected with mononucleosis. However, the study also points out that more than 90 percent of healthy adults are infected with Epstein-Barr virus — a number far below the number of people with multiple sclerosis — and therefore infection alone is clearly not enough to cause multiple sclerosis. More studies will be needed to untangle this correlation.

Treatments

Most treatments for infectious mononucleosis aim to reduce symptoms. Sore throat can be relieved with salt-water gargles, throat lozenges and anesthetic sprays. Patients who want to take painkillers, however, should avoid acetaminophen (such as Tylenol) to avoid stressing out the liver, according to the American Medical Society for Sports Medicine article. Corticosteroids may be helpful in treating complications such as severe swelling of throat and tonsils.

Although infectious mononucleosis is caused by a virus, antiviral drugs such as acyclovir (also known as Zovirax), have not shown to be particularly effective. A meta-analysis of five randomized controlled trials involving 339 patients failed to see significant benefits of the drug compared to placebo. Antibiotics may be used if the patient also has strep throat, according to the Mayo Clinic, though ampicillin or amoxicillin could result in rashes.