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Genital Herpes - Herpes simplex virus

Genital Herpes is caused by herpes simplex virus type l or herpes simplex virus type ll. Both viruses can infect the mouth (producing cold sores) or the genital area (genital herpes).

A blood test for herpes is now available. Many people hope this test will answer important questions they have about herpes.

There are many uncertainties about the test and its results are often difficult to interpret.

Consider the information in this pamphlet and discuss with a doctor whether this test is likely to answer your questions.

Herpes simplex viruses (HSV) cause genital herpes. There are two types of herpes simplex virus and they are referred to as type 1 and type 2. Both types can cause genital herpes. However, type 2 is the usual cause of repeated attacks of genital herpes.

Type 1 HSV can also cause genital infections and tends to produce fewer recurrences than that caused by type 2. Type 1 is the most common cause of cold sores (oral herpes). About 80% of adults in Australia have evidence of infection with type 1 HSV.

Diagnosis

Taking a swab test from a genital sore is the only way to accurately diagnose genital herpes.

If people go to their doctor when a genital sore is not present, a swab test cannot be used for diagnosis.

Blood tests may help to make the diagnosis, but the results can be difficult to interpret.

A blood test for herpes is a test for antibodies, which are produced by the immune system when we are infected with HSV. A blood test tells whether you have ever been infected with the herpes virus. It cannot tell when you became infected.

A blood test does not detect the virus itself.

The herpes blood test cannot tell:

• which part of your body is infected (lips or genitals)

• whether you will develop symptoms of herpes

• if your symptoms are due to herpes.

It may take between six and eight weeks to detect antibodies in a herpes blood test after first becoming infected with HSV. Also, antibodies may disappear with time, especially if the person has infrequent recurrences of herpes.

Negative results for either type 1 or type 2 HSV mean the person has not been infected with either virus in the past.

If a person has a positive result for type 1, they have been infected with type 1 HSV in the past. This is a very common result. Usually the infection is acquired in childhood and is located on the mouth (cold sores). Nowadays, genital herpes infection with type 1 HSV is also a possible explanation.

Positive results for type 2 means the person has been infected with type 2 HSV in the past. A common explanation is that the person has had genital herpes, caused by type 2. Another possibility is that they have cold sores on the mouth caused by type 2 HSV. This is a less common explanation.

• All tests may sometimes give an incorrect result.

• The current test used by our laboratory service gives a positive result in about 5% of people who do not have HSV infection (this is called a false positive result).

• The test will give a negative result in 15% of people who really are infected with HSV (this is a false negative result).

• The herpes blood test varies in its reliability, so the meaning of a test result must be considered along with your medical history.

• A positive blood test simply indicates that the person has been infected with type 1 or type 2 HSV (or both) some time in the past.

• A positive blood test does not indicate the site of the infection.

• Serology tests do not provide any information about whether symptoms (genital or oral) are due to herpes.

• A positive blood test does not tell if the person is infectious at the time of the test.

STD Services web site: stdservices.on.net/std/herpes

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