The prevalence of both genital and oral herpes simplex virus infections has declined steadily since 2000. Still, roughly half of middle-aged Americans are infected.

HSV-1, or oral herpes, causes cold sores around the mouth and face, and sometimes genital sores. HSV-2, genital herpes, is sexually transmitted, and causes sores around the genitals, buttocks and anus. HSV-2 can sometimes cause mouth sores as well.

Both types of herpes are transmitted by direct contact with an infected person; some infected people have no symptoms.

Oral herpes is usually acquired early in childhood or adolescence from nonsexual contact with saliva. It can be spread to the genitals through oral sex. Genital herpes is spread by vaginal, anal or oral sex with an infected person.