Herpes (HSV) 2 IgG Test

HSV2 IgG measures immunoglobulin G antibodies that the immune system produces after exposure to herpes simplex virus type 2. Immunoglobulin G is a long lasting antibody that the immune system creates several weeks after an infection. Once present, these antibodies remain detectable for life. This makes HSV2 IgG a marker of past infection rather than a sign of current viral activity.

Herpes simplex virus type 2 is the primary cause of genital herpes. After the first infection, the virus enters nearby nerve cells and stays in a latent state. Latent means the virus is present but not actively causing symptoms. During this latent phase the immune system continues to maintain IgG antibodies. A positive HSV2 IgG result therefore tells you that the immune system has encountered HSV2 but it does not tell you whether symptoms have ever occurred. Many people carry HSV2 without recognizing any outbreaks because the infection can be mild or entirely silent.

The test relies on a type specific method that detects antibodies targeting glycoprotein G2. Glycoprotein G2 is a protein located on the surface of HSV2 that makes the virus recognizable to the immune system. Modern assays such as enzyme linked immunosorbent assays and immunoblot tests use this target because it reduces confusion between HSV1 and HSV2 antibodies. Specificity refers to how well a test avoids false positive results. Sensitivity refers to how well a test detects true positive results. HSV2 tests usually have high specificity with somewhat variable sensitivity. Accuracy can vary among labs and mild early infections may take several weeks to become detectable.

Population studies show that HSV2 IgG levels vary widely. Some countries have very low prevalence in the general population while others have significantly higher rates. Seroprevalence means the percentage of people in a population with detectable antibodies. Seroprevalence rises steadily with age and is consistently higher in women. Rates also increase with a greater number of sexual partners or a history of other sexually transmitted infections. Individuals with HIV also tend to have higher rates of HSV2 IgG.

Clinically, HSV2 IgG is most useful for understanding prior exposure. It is not a marker of current symptoms. Symptom history alone cannot reliably predict infection because many HSV2 infections are silent. Some people only learn of their infection through routine screening or partner testing. Screening policies vary because testing has value for epidemiology and risk counseling, yet it does not change treatment for people without symptoms. In asymptomatic people, positive results confirm past exposure. In symptomatic people, the test helps differentiate between HSV1 and HSV2 genital infections, which can matter for recurrence patterns and counseling.

Low risk results mean no prior exposure, although very early infections may not yet show antibodies. High results confirm exposure but do not indicate disease severity or frequency of outbreaks. Because HSV2 remains latent in nerve cells, antibody levels do not fluctuate with symptoms and cannot be used to monitor treatment. They reflect the immune memory of exposure.