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.
Infectious mononucleosis (often called mono) is a common viral infection that causes fever, sore throat, and enlarged lymph nodes. Mononucleosis is most commonly caused by the Epstein-Barr virus (EBV), and it is most frequently diagnosed in teenagers and young adults.