What is herpes? Herpes is a term that generally refers to a family of viral infections characterized by painful, fluid-filled sores or blisters in and around the mouth or genital region. Herpes is also called herpes simplex, which includes two types: Genital herpes is a common sexually transmitted disease (STD) marked by outbreaks of blisters and lesions in the genital area. Genital herpes is most often caused by infection of the herpes simplex virus type 2 (HSV-2).About one out of six people 14 to 49 years of age has genital herpes caused by the HSV-2 infection, according to the Centers for Disease Control and Infection (Source: CDC). Another herpes virus, herpes simplex virus type 1 (HSV-1), which generally causes oral herpes, can also cause genital herpes. Oral herpes (herpes simplex labialis) is a very common disease that causes small, painful cold sores and fever blisters of the mouth, lips or gums. Oral herpes is most often caused by HSV-1, but HSV-2 may also be responsible in some cases. It is estimated that 50% to 80% of all American adults have oral herpes, according to the Centers for Disease Control and Infection. HSV-1 and HSV-2 are closely related viruses that belong to a larger family of herpes viruses that can cause a variety of other diseases. Other common types of herpes viruses include cytomegalovirus (CMV), herpes zoster (causes shingles and chickenpox), and Epstein-Barr virus (can cause mononucleosis and other infections). Herpes simplex virus infections are very contagious and can be spread to either the genital or oral areas by direct contact with herpes sores or blisters, or skin, saliva, or mucus membranes infected with a herpes simplex virus. Herpes is not curable, but it is preventable and controllable in many cases. In some cases, herpes can lead to serious complications, such as meningitis, blindness, or death of a newborn that was exposed to the disease during pregnancy or delivery. Seek prompt medical care if you are pregnant or have a disease or condition that suppresses the immune system, and believe that you have been exposed to herpes or have herpes symptoms, such as sores or blisters in the genital or oral area.