Genital herpes, which is usually caused by herpes simplex 2, is extremely common, partly because people with no symptoms can release the virus through their skin, spreading it to sexual partners. About one in five U.S. adults and teens has had a genital herpes infection, studies show. Even when the hallmark genital blisters don’t appear, the stigmatizing condition can cause anxiety and isolation. And a genital infection passed to an infant before, during or after birth can cause disability or death.