Genital herpes simplex is predominantly caused by herpes simplex virus (HSV) type 2 in the United States, although HSV-1 is responsible for 30% of cases of first-episode genital herpes. Because genital herpes associated with HSV-2 is much more likely to recur than is genital herpes caused by HSV-1, more than 90% of recurrent genital herpes is caused by HSV-2. HSV-2 typically presents as erythematous papules that progress to vesicles that ulcerate, leaving fairly tender lesions. The primary infection tends to cause the most severe symptoms, and recurrences are less painful and of a shorter duration than the primary infection.