Mononucleosis (Mono) is one of those illnesses most people are vaguely aware exists but may not know all that much about. Mono causes symptoms that can be confused with a bad cold, the flu, or even COVID-19, making it yet another illness that should be on your radar right now. But what is mono, exactly, and what are the signs that you might have this over any of the other illnesses floating around out there right now? Here's what you need to know. What is mono? Infectious mononucleosis, usually referred to as just "mono," is a contagious disease that's usually caused by the Epstein-Barr virus, according to the Centers for Disease Control and Prevention (CDC). Mono, which is also called "the kissing disease," is usually spread through bodily fluids, with saliva being the most common, the CDC says. Still, it's possible to spread the virus through blood and semen during sexual contact, blood transfusions, and organ transplants. Mono is most common in tee...