Herpes simplex virus can cause symptoms on the mouth (oral herpes) or genitals (genital herpes).
About 50 to 80 percent of American adults have oral herpes, which is commonly called cold sores or fever blisters.
About one in five adults in the United States has genital herpes. However, most people don’t know they are infected because their symptoms are too mild to notice or mistaken for another condition.
Herpes is most easily spread from genital-to-genital or oral-to-genital contact during an active outbreak or during prodrome -- the few days just before an outbreak.
Oral and genital herpes can be uncomfortable, but they are generally not dangerous infections in healthy adults.
Herpes does not affect the immune system. It is rare for adults to have any health problems from genital herpes.
However, having genital herpes makes it easier to acquire and/or transmit HIV, a virus that can cause AIDS.
There are several days throughout the year when herpes can be spread even when no symptoms are present (called asymptomatic reactivation or asymptomatic shedding).
The surest way to prevent the spread of genital herpes is to avoid sexual contact during an active outbreak and to use condoms for sexual contact between outbreaks. Suppressive (daily) antiviral therapy with valacyclovir has also been proven to reduce the risk of transmission to a partner.
Most couples decide together how to reduce the risk.