Mononucleosis

Mononucleosis, also called “mono,” is a common viral illness that can leave you feeling tired and weak for weeks or months. Mono is caused by the Epstein-Barr virus (EBV). It is most often seen in adolescents and young adults. Children can get the virus, but it often goes unnoticed because their symptoms are mild. Older adults usually do not get mono, because they have immunity to the virus.