Herpes (HSV) 2 IgG

Most people who carry genital herpes virus type 2 never know it. They have no visible sores, no flare-ups they can identify, and no reason to suspect anything is wrong. Yet their immune system has been quietly producing antibodies for years, sometimes decades, and they can still pass the virus to a partner.

This blood test reveals that hidden history. By measuring HSV-2 IgG (immunoglobulin G antibodies to herpes simplex virus type 2), it tells you whether your body has encountered the virus at some point in your life, even if you have never had a symptom you recognized as herpes.

What This Test Actually Shows

HSV-2 IgG is a protein your immune system builds specifically against herpes simplex virus type 2, the strain that causes most genital herpes infections. The test targets antibodies against a unique piece of the virus called glycoprotein G-2 (gG-2), which is different enough from HSV-1's version that the test can tell the two strains apart.

A positive result means your body has met the virus and built lifelong immune memory against it. The virus itself never leaves your body once infected. It hides in nerve cells and can reactivate periodically. A negative result usually means no exposure, but it can also mean you were infected too recently for antibodies to have appeared yet, since the window between exposure and a detectable result can run several weeks.

HSV-2 infection is common worldwide. Population studies suggest about 13 out of every 100 people aged 15 to 49 carry the virus, with rates higher in women and in regions of sub-Saharan Africa. Seroprevalence in the United States sits between roughly 12 and 16 percent in recent surveys, and Taiwan and other Asian populations show rates of around 7 to 12 percent.

Genital Herpes You Might Not Know You Have

The most common reason to test is to clarify whether unexplained genital symptoms, or a partner's diagnosis, point to HSV-2. Many infections produce mild or atypical symptoms that get blamed on yeast infections, irritation, or stress. Once people learn they are seropositive and are coached on what reactivations look like, a significant portion begin to recognize episodes they previously dismissed. Studies suggest that up to 85 percent of people who initially report no symptoms but test HSV-2 positive will recognize an outbreak within 6 months once educated about what to look for.

A prospective study of nearly 2,400 sexually active adults found that about 4 in 10 newly acquired HSV-2 infections were symptomatic at the time of acquisition. Combined with the recognition phenomenon above, this means that while many infections appear silent at the moment of acquisition, far fewer remain truly asymptomatic over the long term. Knowing your status changes behavior: it lets you tell partners, consider suppressive antiviral therapy, and recognize reactivations earlier when treatment works best.

HIV Acquisition Risk

Carrying HSV-2 substantially raises your chance of catching HIV if exposed. The virus causes microscopic breaks in genital skin and brings activated immune cells (the very cells HIV targets) to the surface, making transmission easier in both directions.

A meta-analysis pooling longitudinal studies found that people in the general population with established HSV-2 infection were roughly 2.7 times as likely to acquire HIV as those who were HSV-2 negative (adjusted relative risk 2.7, 95% CI 2.2 to 3.4). The risk was even higher for people who newly acquired HSV-2 during the study, who were about 4.7 times as likely to then acquire HIV (adjusted relative risk 4.7, 95% CI 2.2 to 10.1). Earlier analyses separated by sex found that HSV-2 positive men in the general population had about 2.7 times the HIV risk, and women about 3.1 times the risk of their HSV-2 negative counterparts. These estimates already account for age and sexual behavior, so they reflect the biological boost HSV-2 gives HIV rather than just overlap in risk groups.

For anyone with current or future HIV exposure risk, knowing your HSV-2 status matters. It can guide decisions about pre-exposure prophylaxis (PrEP), barrier methods, and suppressive antivirals.

Pregnancy and Neonatal Herpes

A first HSV-2 infection during late pregnancy is one of the more dangerous scenarios for a newborn. With a primary maternal infection acquired near delivery, the risk of transmission to the baby is roughly 30 to 50 percent (and may be as high as 40 to 80 percent in some series), because the mother has not had time to build protective antibodies that cross the placenta. Babies born to mothers with established HSV-2 immunity and high levels of type-specific gG-2 antibodies are far less likely to develop neonatal herpes than babies whose mothers acquired the virus during pregnancy.

This is why HSV-2 status is useful before or early in pregnancy. If you are negative and your partner is positive, you can take steps to avoid acquisition during pregnancy. If you are positive, your obstetric team can monitor for and treat reactivations near delivery.

Dementia Risk: A Mixed but Real Signal

Herpes viruses have been linked to long-term brain health, though the evidence is uneven. A Swedish cohort of 1,002 dementia-free 70-year-olds followed for 15 years found that adults carrying anti-HSV IgG antibodies were more than twice as likely to develop dementia compared with non-carriers (hazard ratio 2.26), an association that held after accounting for sex, education, and APOE ε4 genotype, the strongest genetic risk factor for Alzheimer's.

A much larger nationwide Korean cohort of 752,205 adults aged 45 or older followed from 2006 to 2017 found that people with a clinical diagnosis of HSV infection had about 38 percent higher risk of developing any dementia compared with those without (hazard ratio 1.38, 95% CI 1.33 to 1.43), after adjusting for age, sex, and other illnesses. Co-infection with HSV and varicella zoster virus pushed the risk higher still.

A 2025 meta-analysis of 32 studies tempered these findings. When the pooled evidence relied on antibody status alone rather than clinical infection episodes, the dementia association weakened considerably. The link is real enough to take seriously but is not strong or consistent enough to predict dementia from HSV-2 IgG alone. Knowing your status is more useful as one input into broader brain-health planning than as a standalone risk score.

Metabolic Health and Diabetes Risk

A German prospective cohort of 1,257 adults with normal glucose tolerance at baseline followed for about 7 years found that HSV-2 seropositivity independently predicted developing prediabetes or diabetes. The association held after accounting for sex, age, body mass index, education, smoking, physical activity, parental diabetes, blood pressure, lipids, insulin resistance, and fasting glucose, a thorough set of adjustments suggesting the link is not just confounded by overlapping risk factors.

This does not mean HSV-2 causes diabetes in any direct way. It does suggest that chronic viral burden may add to the metabolic stress your body manages over decades, which is one more reason to know your status if you are thinking about long-term metabolic health.

Cardiovascular Findings

In HIV-positive men followed in the Multicenter AIDS Cohort Study (291 participants), HSV-2 positivity was associated with greater subclinical coronary atherosclerosis (adjusted odds ratio 4.12, 95% CI 1.58 to 10.85), suggesting the chronic immune activation from herpes viruses may contribute to vascular disease in immunocompromised people. Population-based data are consistent with a broader signal: a U.S. NHANES analysis linked HSV-2 seropositivity to premature cardiovascular disease (odds ratio 1.56, 95% CI 1.09 to 2.21), and a meta-analysis found a modestly elevated atherosclerosis risk with HSV-2 (odds ratio 1.37, 95% CI 1.13 to 1.67). The effect outside HIV-positive populations is real but smaller and more variable.

Test Accuracy and the Low-Positive Trap

Performance of type-specific HSV-2 IgG ELISA assays (a lab method that measures antibody binding) varies substantially by platform. Newer automated assays such as Roche Elecsys and Bio-Rad BioPlex achieve sensitivity above 97 percent and specificity above 98 percent for HSV-2 IgG. The most widely used older assay, the HerpeSelect EIA, has high sensitivity (around 99 percent) but pooled specificity of only about 81 percent (95% CI 68 to 90 percent), and in U.S. populations its positive predictive value can be as low as 50 percent. Index values just above the cutoff, roughly 1.1 to 3.0 on the HerpeSelect assay (some studies extend this to 3.5), carry a particularly high rate of false positives when compared against the gold-standard Western blot test.

This matters because a single low-positive result can be misleading. If your initial result lands in this borderline zone and you have no symptoms or known exposure, the appropriate next step is confirmatory testing on a different platform rather than accepting the diagnosis at face value. Largely because of these test-performance issues, the U.S. Preventive Services Task Force recommends against routine serologic screening for genital herpes in asymptomatic adolescents, adults, and pregnant people (a Grade D recommendation), citing poor specificity, limited confirmatory testing, and no clear evidence that screening improves health outcomes. Targeted testing in people with symptoms, exposures, or specific risk factors is a different question and remains clinically useful.

Why IgM Testing Is Usually Not the Answer

A common misconception is that HSV-2 IgM antibodies signal a recent infection. They do not, at least not reliably. The CDC and IDSA explicitly recommend against IgM testing for HSV because the tests are not type-specific and can be positive during reactivations of long-established infections, persisting years after the initial exposure. Some studies suggest IgM is detectable in roughly 3 out of 10 people with chronic, well-established HSV-2 infection.

If you want to know whether a recent exposure led to a new infection, the more reliable approach is to retest IgG at the right time. Antibodies usually become detectable about 2 to 6 weeks after exposure but can take up to 3 months. Document a negative baseline, then retest at 3 months after the potential exposure.

Tracking Over Time

Unlike a cholesterol number that moves with diet and medication, HSV-2 IgG is essentially binary at any given moment: either you have been infected or you have not. Once you are clearly positive, retesting does not provide new information about the same infection. The titer (how much antibody you have) is not a measure of severity, contagiousness, or how recently you were infected.

That said, your status can change in one direction: negative to positive. If you are HSV-2 negative and remain sexually active, retesting after a new partner or a known exposure is reasonable, though routine screening of asymptomatic adults is not recommended. If you started with a borderline result, retest in 8 to 12 weeks on a different assay to confirm. If you are confirmed positive, your IgG number is settled. Future monitoring should focus on companion tests such as HIV screening, broader sexually transmitted infection panels, and, in pregnancy, careful obstetric planning.

Decision Pathway for an Unexpected Result

A clearly positive result (high index value) in someone with symptoms or known exposure usually does not need confirmation. Next steps are practical: discuss suppressive antiviral therapy if recurrences are frequent or you have an HSV-2 negative partner, get tested for HIV and other sexually transmitted infections, and tell sexual partners. If you are planning pregnancy, raise this with your obstetric provider.

A low-positive result without symptoms warrants confirmatory testing, ideally with Western blot or a second high-quality ELISA. Until that is done, treat it as uncertain rather than definitive.

A negative result after a known exposure should be repeated at the 12-week mark, since seroconversion can be delayed. A negative result in someone with classic recurrent genital symptoms should prompt direct testing of any active lesion with PCR, which can detect the virus itself when serology has not yet turned positive.

When Results Can Be Misleading

• Window period: if you test within several weeks of a new exposure, you may not have produced detectable antibodies yet. A negative result this early does not rule out infection.
• Borderline index values: low-positive results in the index 1.1 to 3.0 range on the HerpeSelect assay (some studies extend this up to 3.5) have a substantial false-positive rate when checked against Western blot, with roughly 60 percent of results in this zone being false positives. Confirm before accepting the diagnosis.
• Assay differences: older platforms like the HerpeSelect EIA have meaningfully lower specificity than newer automated assays (such as Roche Elecsys or Bio-Rad BioPlex). If you are unsure which platform was used, ask, especially for a borderline result.
• HSV-1 cross-reactivity: some assays show reduced specificity in people who are already HSV-1 positive, occasionally producing weak HSV-2 positives that do not reflect real infection.
• Rapid point-of-care tests: quick HSV-2 antibody tests can have poor specificity. A positive result on a rapid test should be confirmed by a laboratory ELISA before any clinical decision.

Common chronic medications such as statins, metformin, GLP-1 agonists (drugs like semaglutide that lower blood sugar and appetite), PPIs (proton pump inhibitors used for reflux), thyroid medications, and steroids have not been shown to systematically distort HSV-2 IgG results. Acute factors like recent exercise, fasting, illness, or time of day also do not meaningfully affect this antibody, which reflects months to years of immune memory rather than acute physiology.