Herpes simplex virus (HSV) is a virus that causes infections and is categorized into two types: HSV-1 (oral herpes) and HSV-2 (genital herpes) . HSV-2 affects an estimated 491 million people aged 15-49 years worldwide. HSV-2 infects women almost twice as often as men because sexual transmission is more efficient from men to women. Genital herpes infections can be asymptomatic, or can show up as outbreaks of blisters or sores. HSV-2 is mainly transmitted during sex through contact with genital or anal surfaces, skin, sores, or fluids of someone infected with the virus. HSV-2 can be transmitted even if the skin looks normal and is often transmitted in the absence of symptoms. In rare cases, infection with HSV-1 or HSV-2 can lead to meningitis or encephalitis.

HSV-1 is mainly transmitted via contact with the virus in sores, saliva, or surfaces in or around the mouth. Less commonly, HSV-1 can be transmitted to the genital area through oral-genital contact to cause genital herpes. It can be transmitted from oral or skin surfaces that appear normal; however, the greatest risk of transmission is when there are active sores. People who already have HSV-1 are not at risk of reinfection, but they are still at risk of acquiring HSV-2.

HSV-2 infection increases the risk of acquiring HIV infection by approximately three-fold. Additionally, people with both HIV and HSV-2 infection are more likely to spread HIV to others. Pregnant women with genital herpes should talk to their doctor, as genital herpes can be passed on to the baby during childbirth.

HSV-1 and HSV-2 can be diagnosed through a physical exam and laboratory tests, and antiviral medications can be used to treat outbreaks and reduce the frequency of recurrences.