Q: What causes mono?
A: Mononucleosis (mono) is an infectious disease that causes an increase in monocytes (a type of single nucleus white blood cell that can engulf bacteria/foreign particles/small cells). It is usually passed from person to person through the exchange of saliva, whether from kissing (so it is sometimes called the kissing disease) or sharing a glass/utensil. It can also be transmitted from sneezes, coughs or in other ways. Although it is an infectious disease, it is actually not as contagious as the common cold or certain other viruses.
About 90 percent of cases of mono are due to infection with the Epstein-Barr Virus (EBV). The other cases are due to the other viruses (cytomegalovirus, one of the hepatitis viruses, rubella, HIV, adenovirus, others), toxoplasmosis (due to the parasite Toxoplasma gondii) or possibly other infectious agents. When it is due to EBV, symptoms typically manifest after a four to six-week incubation period (while the virus multiplies in the patient).
Although many cases of EBV infection have minimal or no symptoms (especially in very young kids who may only manifest a low-grade fever), the combination of fever, swollen glands (in the neck, armpits or other location) and a sore throat (with enlarged and inflamed tonsils) are the classic presentation of infectious mono. In addition, adolescents and young adults may also have headache, body aches, skin rash, fatigue (which can be quite pronounced) and/or other symptoms. About two thirds of patients also develop an enlarged spleen (an organ in the left upper quadrant of the abdomen that supports red blood cell production/clearance as well as being vital to the body’s immune system).
Although uncommon, complications from mono may occur. These may include rupture of the spleen (this occurs in only one or two per thousand symptomatic patients, sometimes from trauma as the enlarged spleen is more susceptible to rupture, or possibly spontaneously), inflammation of the liver (hepatitis, which may lead to yellowing of the skin/white part of the eyes called jaundice, and even liver function compromise), anemia (low red blood cell count), low platelet count (which can lead to abnormal bleeding), heart problems, and/or others. If the patient’s mono is caused by HIV, a hepatitis virus, or other infectious agent then complications from the causative disease may also occur. There may also be a small increased risk for certain types of lymphoma, and/or other cancers.
Mono is typically diagnosed based on the symptoms and physical exam. In some cases a blood test may be done to verify the diagnosis. This may include a complete blood count (which would show the increase in monocytes), as well as a more specific test to look for antibodies to EBV (called a mono-spot test).
The symptoms of mono typically resolve on their own; the sore throat and fever usually improve over days to a couple of weeks and the enlarged spleen and swollen glands over 3 to 4 weeks. However, the fatigue often last longer, and may take a few months (or even several months) to resolve.
Supportive care includes avoidance of sports/traumatic contact (to minimize the risk of rupture until the splenic enlargement resolves), rest (and patience while the fatigue runs its course), fluids by mouth and symptomatic treatments (such as over-the-counter medications for fever or pain). Interestingly, there may be an idiopathic reaction to certain antibiotics (specifically in the penicillin family, which may be erroneously prescribed for the fever and sore throat thinking the patient may have strep throat), so these medications should be avoided.
There is no vaccination to prevent mono, so avoiding saliva exposure from someone who has mono is advised. This is often challenging as the EBV may persist in a patient’s saliva for 6 months (or even more).
Over 95 percent of American adults have antibodies to EBV, indicating that they have been exposed to it (whether symptomatic or not) at some point in their lives. EBV infection is thought to give lifelong immunity to reinfection.
Jeff Hersh, Ph.D., M.D., can be reached at DrHersh@juno.com