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.
Mono or Infectious mononucleosis is usually caused by the Epstein-Barr virus. The virus is not as infectious as a common cold. It can, however, be transmitted to another person by cold symptoms such as sneezing and coughing. Infectious mononucleosis, often colloquially called the kissing disease, can be transmitted literally through kissing or contact with saliva of an infected person. Though mononucleosis itself isn't usually very serious, complications arising out of it may be a cause for concern.