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Blood Test Tracker

Herpes Simplex Virus 2 IgG (Type-Specific)

Looks for IgG antibodies to herpes simplex virus type 2 (HSV-2), a common cause of genital herpes. A low positive result often needs a second test to confirm.

AI-verified against cited sources. Awaiting expert reviewAlso called HSV-2 IgG, HSV2 IgGLOINC 7912-9

What it is

Herpes simplex virus type 2 (HSV-2) is a common virus that is usually spread through sexual contact. Many people with HSV-2 have no symptoms or very mild ones and never know they have it. After infection, the body makes IgG antibodies, which this test finds using a protein (glycoprotein G) that lets it tell HSV-2 from HSV-1. Many labs report a number called an index value next to a negative, equivocal or positive label. In a US government survey, about 12% of people aged 14 to 49 had HSV-2 antibodies in 2015 to 2016.

Why it matters

A blood test can show whether you have been infected with HSV-2 even if you have never had symptoms. CDC says it is useful for people with repeated or unusual genital symptoms whose swab test was negative, for people given a clinical diagnosis without lab confirmation, and for people whose partner has genital herpes. CDC does not recommend routine HSV-2 blood screening in the general population or during pregnancy, partly because low positive results are often wrong. If you have a sore, a swab test of the sore is the usual way to find the cause.

If it’s high

A positive result means HSV-2 antibodies were found, which usually points to a past or ongoing HSV-2 infection. The test cannot tell when you were infected, where on the body, or whether you will have symptoms. Results close to the cutoff, called low positives, are often false positives. CDC says index values from 1.1 to 3.0 on one common test are frequently wrong, and that a second type of test should be used to check them.

Common causes

  • An HSV-2 infection from the past, often without noticeable symptoms
  • A current HSV-2 infection, with or without symptoms
  • A false-positive low index value, which can happen with HSV-2 antibody tests

What can help

  • Ask your clinician whether a low-positive result should be checked with a second type of test
  • Ask what the result means for you and for any partners
  • If you are pregnant or planning pregnancy, ask what a positive result means for your care
  • If you have symptoms, ask about treatment options

What can affect your result

  • Index value: low positives are often false positives
  • Time since infection: antibodies take weeks to appear, and false negatives are more common early
  • Test brand: cutoffs and equivocal zones differ
  • Age and sex: positive results become more common with age and are more common in women in US data (about 16% of females and 8% of males aged 14 to 49)
  • An HSV-2 test does not detect HSV-1, and an HSV-1 test does not detect HSV-2
  • Low index values are often false positives. CDC reports that in one study, a widely used HSV-2 test had a specificity of 57.4% overall and 39.8% for index values from 1.1 to 2.9.
  • Testing soon after infection can be negative, because antibodies take weeks to appear. For a suspected recent infection, CDC advises repeating the antibody test 12 weeks after the presumed time of acquisition.
  • Each test brand sets its own index cutoffs and equivocal zone, so check the range printed on your report.

Antibodies take weeks to appear after infection. Herpes is a lifelong infection, and the antibodies generally stay detectable.

When to talk to a clinician

Seek care promptly for painful blisters or sores in the genital area, trouble passing urine, or a fever with them. If you are pregnant and have symptoms, or your partner has genital herpes, tell your care team early. Get urgent care for a severe headache with fever and confusion, or if a newborn has blisters, fever or poor feeding.

Questions you could ask

  • Is this test useful for me, given my symptoms and history?
  • Is my index value high enough to trust, or should we confirm it with a second test?
  • What does this result mean for me and for any partners?
  • If I was exposed recently, should I repeat this test later?

Questions people ask

Why might a low positive result be wrong?

On some tests, results just above the cutoff are often false positives. CDC reports that in one study, a widely used test had a specificity of about 57% overall and about 40% for index values of 1.1 to 2.9. For this reason, CDC says to confirm low values with a second type of test before deciding what they mean.

Should I be tested if I have no symptoms?

CDC does not recommend HSV-2 blood tests for screening the general population. Testing can be useful in some situations, for example if a partner has genital herpes. Talk with your clinician about whether testing makes sense for you and what you would do with the result.

How soon after a possible exposure can this test show it?

Antibodies take time to show up, so a test done too soon can be negative. For a suspected recent HSV-2 infection, CDC advises repeating the antibody test 12 weeks after the possible exposure.

Show the science and sources

For clinicians and researchers

Type-specific assays detect IgG to glycoprotein G (gG) of HSV-2 and most report an index value with manufacturer-specific cutoffs. CDC (2021) states that the sensitivity of gG type-specific tests for HSV-2 antibody varies from 80% to 98%, with false negatives more frequent early in infection. It notes that the widely used HerpeSelect HSV-2 EIA is often falsely positive at low index values (1.1 to 3.0), with an overall specificity of 57.4% and 39.8% for index values of 1.1 to 2.9 in one study. CDC says low index values should be confirmed with a second method (for example Biokit or Western blot) before interpretation, and that the HerpeSelect immunoblot should not be used for confirmation because it uses the same antigen. CDC lists HSV-2 serology as useful for recurrent or atypical genital symptoms with a negative PCR or culture, a clinical diagnosis without lab confirmation, and a partner with genital herpes. CDC advises repeating antibody testing 12 weeks after a presumed recent acquisition, and does not recommend HSV-2 serologic screening of the general population or of pregnant women. NCHS (NHANES 2015 to 2016) found HSV-2 seroprevalence of 11.9% in people aged 14 to 49 (0.8% at ages 14 to 19, 7.6% at 20 to 29, 13.3% at 30 to 39 and 21.2% at 40 to 49), with 15.9% in females and 8.2% in males after age adjustment. This file does not encode index cutoffs because they differ by manufacturer.

LOINC 7912-9 (primary), 17851-7, 5209-2, 43180-9. Specimen: serum.

Sources

  1. Sexually Transmitted Infections Treatment Guidelines, 2021: Genital Herpes, CDC (2021)
  2. Prevalence of Herpes Simplex Virus Type 1 and Type 2 in Persons Aged 14-49: United States, 2015-2016 (NCHS Data Brief No. 304), National Center for Health Statistics, CDC (2018)

AI-verified against cited sources. Awaiting expert review. Last reviewed 2026-10-03. How we build and check these pages.

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