How Long Does A Herpes Outbreak Last. Genital herpes is a sexually transmitted disease (STD). Women are more commonly infected than men. For women who have sores, the first outbreak may last two to four weeks.Another outbreak can occur in weeks or months.One in five American adults has herpes, but only one third of those inflicted are aware that they have the virus.enital herpes is a sexually transmitted disease (STD). Women are more commonly infected than men. For women who have sores, the first outbreak may last two to four weeks.