Key facts Herpes simplex virus, or herpes, is of two types: herpes simplex virus (HSV-1) and herpes simplex virus of the second type (HSV-2). HSV-1 is transmitted primarily through the oral contact and causing oral herpes (whose symptoms may be in the form of "cold lips"), but also may cause and genital herpes. HSV-2 is one of infections, sexually transmitted infections, and causes genital herpes. Both forms of HSV-1 and HSV-2 cause lifelong infection. It is estimated that worldwide HSV-1 infected about 3.7 billion people under the age of 50 years (67% of the population). It is expected that the worldwide HSV-2 infected about 417 million people aged 15 to 49 years (11%). Most cases of oral and genital herpes are asymptomatic. Herpes symptoms include painful vesicles or ulcers in the infected area. Herpes infection is most contagious during the presence of symptoms, but can be transmitted, and in their absence. Infection with HSV-2 increases the risk of infection and transmission of HIV.