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.
Causes of Mononucleosis: Mono is caused by Epstein Barr virus. Inadequate nutrients and lack of vitamins in the body are the main causes for this disease. When the body does not get the required vitamins and essential nutrients, the immune system becomes weak and persons with weak immune system are an easy prey for Epstein Barr virus.