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.
EBV is the most common cause of infectious mononucleosis, but other viruses can cause this disease. Typically, these viruses spread most commonly through bodily fluids, especially saliva. However, these viruses can also spread through blood and semen during sexual contact, blood transfusions, and organ transplantations.pstein-Barr virus (EBV) is the most common cause of infectious mononucleosis, but other viruses can also cause this disease.