Diagnosis of Herpes

How do I know if I have herpes?

It is easy to know that you have herpes if you get cold sores or recurrent genital herpes. Cold sores are often triggered by stress or excessive sunshine (skiing, sunbathing). Some women may also experience cold sores associated with menstruation. Genital herpes may also be triggered by stress, menstruation, or mechanical trauma during intercourse. Interestingly only approximately a quarter to a third of HSV-1 infected individuals get cold sores or recurrent genital herpes. The reason for this variation between HSV infected individuals is unknown, but likely reflects genetic differences in infected people.

Diagnosis of cold sores

The clinical diagnosis of a cold sore is often straightforward. It can be less clear when chronic cold sores occur in immunocompromised patients or when the cold sore spreads in patients with eczema. Laboratory diagnosis can be done by virus culture or using a rapid detection technique such as immunofluorescence or PCR.

Diagnosis of genital herpes:

The clinical diagnosis of genital herpes may be difficult and laboratory investigations may be necessary.

Can the laboratory help me to diagnose herpes?

There are several laboratory investigations that are helpful to determine whether an individual has been infected by HSV. These investigations also show whether the type of infection is from HSV-1 or HSV-2.

Firstly, the laboratory can measure herpes antibodies in serum (blood). Secondly, the laboratory can detect the virus itself in a variety of body fluids such as eye secretions, mouth secretions, blister fluid, genital secretions, urine, blood and, in very sick patients, the cerebrospinal fluid.

Antibody detection is useful to determine whether a primary HSV infection is happening, in which case HSV IgM antibodies and HSV IgG antibodies will be present. If only HSV IgG antibodies are present, this is a sign of previous infection. By measuring these antibodies in large groups of people, we know that most people who have been infected do not have continuing clinical symptoms in the form of cold sores or genital herpes.

If no HSV antibodies are present in the blood, this means that the individual is not infected or, in rare circumstances, has just been infected and has not had time to make antibodies.

It is also possible, using a more sophisticated and expensive antibody tests (Western blot), to determine whether the detected HSV IgG antibodies are directed specifically against HSV-1 or HSV-2 or both. In other words, the laboratory can determine, through a simple blood test, if an individual has labial and/or genital herpes. Recently, a few “point of care” tests have been marketed, which are based on the same principle as Western Blot. Although these tests can distinguish between HSV-1 and HSV-2 antibodies, they are not as reliable as the Western blot test, which remains the confirmatory test.

Laboratory detection of the virus can be done in several different ways:

The virus can be cultured. This is a labor intense methodology, which requires expertise and will take on average 3-7 days from the time the specimen was collected.

The virus can also be detected by rapid methods, such as immunofluorescence testing (IF) and enzyme linked immunosorbent assays (ELISA), which will give same day results. These tests require specialized laboratories and utilize monoclonal antibodies directed against HSV-1 and HSV-2 respectively. They can, therefore, rapidly distinguish between the presence of HSV-1 and HSV-2.

Recently, exquisitely sensitive laboratory techniques, based on the molecular detection of viral genetic material (DNA) have been developed. Polymerase chain reaction (PCR) is a technique which allows the detection and multiplication of selected parts of the viral DNA so that thousands of copies are made. These can then be detected by standard measurement techniques.

It is by using these tests that we know that some individuals, who do not have known symptomatic oral or genital herpes, may excrete the virus unknowingly (viral shedding).

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