Test Overview
Herpes tests are done to find out if you have been exposed to the herpes simplex virus (HSV). An HSV infection can cause small, painful sores that look like blisters on the skin or the tissue lining (mucous membranes) of the throat, nose, mouth, urethra, rectum, and vagina. A herpes infection may cause only a single outbreak of sores. But in many cases the person will have more outbreaks.
The United States Centers for Disease Control and Prevention (CDC) does not recommend getting a herpes blood test as part of a regular screening for sexually transmitted infections (STIs). That's because a positive result only means you have been exposed to the virus. The test can't tell if you will get sores or if any sores you have are caused by the herpes virus. The test also can't tell if you can infect another person.
There are two types of HSV.
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HSV type 1 causes cold sores (also called fever blisters) on the lips. HSV-1 is generally spread by kissing or by sharing eating utensils (such as spoons or forks) when sores are present. HSV-1 can also cause sores around the genitals.
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HSV type 2 causes sores in the genital area (genital herpes), such as on or around the vagina or penis. HSV-2 also causes the herpes infection seen in babies who are delivered vaginally in women who have genital herpes. HSV-2 is generally spread by sexual contact. HSV-2 can sometimes cause mouth sores.
In rare cases, HSV can infect other parts of the body, such as the eyes and the brain.
Tests for HSV are most often done only for sores in the genital area. The test may also be done using other types of samples, such as spinal fluid, blood, urine, or tears. To see whether sores are caused by HSV, different types of tests may be done.
- Herpes viral culture. This is a test to find the herpes virus. Fluid from a fresh sore is added to certain cells used to grow HSV. If no virus infects the cells, the culture is negative. If the herpes virus infects the cells, the culture is positive. The culture often fails to find the virus even when it is present (false-negative results).
- Polymerase chain reaction (PCR) test. A PCR test can be done on cells or fluid from a sore or on blood or on other fluid, such as spinal fluid. PCR finds the genetic material (DNA) of the HSV virus. This test can tell the difference between HSV-1 and HSV-2.
- Antibody tests. Blood tests can find antibodies that are made by the immune system to fight a herpes infection. Antibody tests are sometimes done but are not as accurate as a viral culture at finding the cause of a specific sore or ulcer. Antibody tests can't always tell the difference between a current active herpes infection and a herpes infection that occurred in the past. Because antibodies take time to develop after the first infection, you may not have a positive antibody test if you have just recently been infected. Some blood tests can tell the difference between HSV-1 and HSV-2.
