HSV-1 usually appears on the mouth or lips as cold sores, or "fever" blisters. This common virus, which affects 20-40 percent of the U.S. population, is not considered an STD and is not normally the cause of genital herpes. However, during oral sex the virus can be transferred to the genitals. In fact, over 30 percent of genital herpes cases in the U.S. are the result of HSV-1.
HSV-2, the more serious of the two viruses, can occur on the mouth, but it typically affects the body in the form of blisters on or around the genitals, anus or rectum. HSV-2 is the main cause of genital herpes, though, as mentioned above, HSV-1 can play a part in contracting the virus.
