Cause

Genital herpes can be caused by either the herpes simplex virus type 1 (HSV-1) or the herpes simplex virus type 2 (HSV-2). HSV-1 or HSV-2 can cause sores on the lips (cold sores) and sores on the genitals. HSV-1 more often causes cold sores. HSV-2 more often causes genital sores. HSV-1 causes up to 50% of primary genital herpes infections. Genital herpes caused by HSV-1 has a lower rate of recurrence than that caused by HSV-2.¹

How the herpes virus is spread

The same virus that causes genital herpes also can cause cold sores (herpes labialis). So HSV can be spread from a genital sore to the lips or from a cold sore to the genital area. HSV can be spread to or from the genitals, anus, or mouth during sexual activities or through any direct contact with herpes sores. You become infected when the virus enters your body through a break in the skin or through moist areas (mucous membranes) such as the mouth, anus, and vagina. Even very small breaks in the skin allow the virus to infect the body.

Newborns can be infected with HSV at birth. This usually happens when a woman has her primary outbreak (the first time she is infected with HSV) close to the time of delivery and the baby is delivered through the vagina. Usually in these cases the woman either does not have symptoms or is unaware of symptoms. The chance of passing the virus to the baby is greatly reduced (less than 1% of the time) during recurrent outbreaks, which occur after a woman has been infected previously.¹ Babies infected with the virus at birth are at risk for serious health problems.

Contagious period

You are most likely to spread HSV when you have a sore or blister during either a primary or recurrent outbreak. But many people who have genital herpes have time periods (a week before and a week after an outbreak) when they can spread the virus even though they do not have blisters or sores present. Some people can spread the infection when they do not recognize that they have a genital herpes sore or when they have symptoms (such as painful urination) that are not typical of genital herpes.