Mononucleosis

Mononucleosis, also known as “mono” or infectious mononucleosis is a condition caused by certain viruses that infect immune cells resulting in the formation of abnormally large and weirdly shaped immune cells.

The virus most responsible for mono is the Epstein-Barr virus (EBV). Epstein-Barr loves to find its way into your body by way of the oropharynx, i.e., your mouth and throat. This is often why mono is called the kissing disease, as infected saliva passed from one person’s oropharynx to another’s is the preferred method for its spread. It can also be just as easily spread by sharing beverages or any other way spit can get from one person to another.  

The classic findings are usually seen in teenagers as often the younger a person is infected with EBV, the fewer signs they show. Those high schoolers who have engaged in mono–make out sessions will often develop fever, fatigue, and sore throat, often with swelling of the throat lymph nodes/glands (leading to its other historical name of glandular fever). In clinic, I will also need to check the spleen of kids and teens with mono. The spleen, you see, is sort of our body’s blood filter. With mono, it has a lot of work to do filtering the blood with these super big reactive immune cells. This can cause the spleen to swell up super big. And when the spleen is all swollen, if it is hit too hard like with a projectile ball from soccer, a fall on the stomach, or the handlebars on a bike, then the spleen can rupture causing a medical emergency of internal bleeding. So we often have teens with mono come back to the clinic in a couple of weeks to make sure their spleens have returned to normal size and they are safe to return to activities that may result in trauma to their abdomen.   

A person’s natural immune system will eventually beat back this infection, but unfortunately, the fatigue in some people can last for months. 

Also, Epstein-Barr virus is in a class of viruses that can live dormant in your immune system for the rest of a person’s life once infected, leading to the possibility of reactivation syndrome if your body’s Hodor (game of thrones anyone?) of an immune system can’t (sorry spoiler) “hold the door” to prevent the virus from replicating and infecting more immune system cells. Thus we see reactivation in people who are trying to burn the candle at both ends or get knocked down from another infection like the flu or COVID.  

 Well how do you protect yourself from the Epstein-Barr virus? Well that is the thing, you see. You don’t really. By the time most people exit high school, 95% of them have been infected by EBV at some point in their lives, most likely when they were little kids and thus never really showed too many symptoms.