Caused by a common virus called herpes simplex (HSV-1), cold sores are contagious and can spread from person to person through skin-to-skin contact or by sharing items (such as eating utensils, lip balm, towels, cosmetics, and food), even when they aren't visible.
Infectious mononucleosis, or mono, refers to a group of symptoms usually caused by the Epstein-Barr virus (EBV). It typically occurs in teenagers, but you can get it at any age. People with mono often have a high fever, swollen lymph glands, and a sore throat.
Mononucleosis is usually caused by the Epstein-Barr virus (EBV). Symptoms usually include fever, swollen and painful tonsils, and enlarged lymph nodes. Fatigue and low energy can last for weeks or months. More than 90% of us eventually catch EBV, usually during adolescence or early adulthood.