You can test for genital herpes by swabbing a genital ulcer and studying it in the laboratory, or by testing for antibodies in the blood.

Genital herpes is caused by the herpes simplex virus (HSV). There are two types, HSV-1 and HSV-2. HSV-1 more commonly causes oral infections (cold sores) and HSV-2 more commonly causes genital herpes. However, genital herpes from HSV-1 is becoming more common.

People who have never had oral HSV-1 infections can get HSV-1 genital herpes through oral sex with someone who has an oral HSV-1 infection. The transmission of herpes from one person to another occurs quickly in new relationships. One study showed that it took 3.5 months, on average, for the uninfected partner to get genital herpes.

About 20% of sexually active Americans have been infected with genital herpes. Most of them never know they have been infected because they do not have ulcers. But even without symptoms, they can pass the infection on to their sexual partners. About one-third of people who become infected with genital herpes develop painful ulcers that may come and go over time. People who have had oral HSV-1 infections who become infected with genital HSV-2 are less likely to get ulcers.

If you get a genital ulcer, your doctor can swab it, and send the specimen to the lab. It will be tested for HSV-1 or HSV-2 by viral culture, polymerase chain reaction, or direct fluorescent antibody testing.

You can also tell if you are infected with herpes through blood testing. Antibodies develop within a few weeks after a person becomes infected with herpes, and they persist for life. A blood test can distinguish between HSV-1 and HSV-2. The presence of HSV-2 antibodies confirms genital infection, but HSV-1 antibodies can be due to either oral infection or genital infection.

At this time, routine screening for HSV antibodies is not recommended. The decision to do any testing for HSV depends upon a person's individual circumstances.