Herpes
Herpes (Greek herpein, “to creep”), name applied to several types of skin eruptions characterized by formation of blisters. The term embraces primarily two distinct disorders, herpes simplex and herpes zoster, both caused by types of herpesviruses. Other herpesviruses include Epstein-Barr virus, the cause of infectious mononucleosis (see Mononucleosis, Infectious ) and cytomegalovirus, which can lead to birth defects when the virus invades pregnant women. Together, these viruses are estimated to cause more human illnesses than any other group of viruses. HERPES SIMPLEX Two types of herpes simplex are known. The first causes cold sores or fever blisters—an eruption of blisters that often occurs during the course of or after one of a variety of diseases associated with fever (most commonly colds, influenza, and pneumonia). The blisters usually appear around the mouth and on the lips (herpes labialis); about the nose, face, and ears; and in the mouth and pharynx. The causative virus has