Herpes 1 and 2 IgG Test

Herpes simplex virus is one of the most common infections on the planet, yet most people who carry it have no idea. Roughly half of American adults have been infected with type 1, and about one in eight carry type 2. The majority were never diagnosed because they never had a visible outbreak, or their symptoms were mild enough to miss. A type-specific antibody test is the only way to know your status when you have no active sores to swab.

This panel measures two separate antibodies, one for each herpes simplex virus type. Knowing which type you carry changes what to expect: how often outbreaks recur, where they are most likely to appear, and how to reduce the chance of passing the virus to a sexual partner or a newborn. A single "herpes test" that does not distinguish between the two types leaves you with an incomplete answer.

What This Panel Reveals

Each test detects a long-lasting antibody (called IgG) that your immune system produces after it encounters a specific strain of herpes simplex virus. IgG antibodies typically appear within two to twelve weeks of infection and remain in your blood for life. A positive result means your body has been infected at some point, even if you have never had symptoms.

Herpes simplex virus type 1 (HSV-1) has historically been associated with oral cold sores, but it now accounts for a growing share of new genital herpes cases, particularly in young adults. Herpes simplex virus type 2 (HSV-2) is almost exclusively transmitted through sexual contact and is the leading cause of recurrent genital herpes. Knowing which type you have determines the likely location of future outbreaks and the pattern of viral shedding, meaning periods when the virus is active on the skin without visible symptoms, that drives transmission.

Why Both Types Matter

HSV-1 and HSV-2 behave differently in the body. Genital HSV-2 recurs roughly four to six times per year on average in the first year after infection, while genital HSV-1 recurs far less often, averaging about once per year or less. That distinction shapes decisions about daily antiviral therapy: someone with frequent HSV-2 recurrences may benefit from suppressive medication, while someone with genital HSV-1 may not need it.

HSV-2 infection also carries an independent health risk beyond outbreaks. A large systematic review and meta-analysis of longitudinal studies found that people with HSV-2 have approximately a threefold increased risk of acquiring HIV compared to those without HSV-2. This association holds even in people who have never had a symptomatic outbreak, because the virus causes invisible changes in genital tissue that make HIV transmission easier.

For pregnant women, knowing your HSV status is especially relevant. A first episode of genital herpes near the time of delivery carries a risk of neonatal herpes as high as 30% to 50%, while the risk from a recurrent infection is much lower, estimated at roughly 2%. If you know your status before pregnancy, your clinician can plan accordingly.

How to Read Your Results Together

Each test reports an index value. A value below 0.90 is considered negative, 0.90 to 1.10 is equivocal, and above 1.10 is positive. But the index number itself carries important nuance. Low positive values between 1.1 and 3.5 on widely used screening blood tests have a meaningful false positive rate, particularly for HSV-2. If your HSV-2 IgG index falls in that range, confirmatory testing with a more precise laboratory method is recommended before accepting the result as a true positive.

When Results Can Be Misleading

The biggest pitfall with HSV IgG testing is timing. If you were exposed within the past two to twelve weeks, your body may not have produced enough IgG antibodies to register on the test. This "window period" means a negative result shortly after a possible exposure does not rule out a new infection. Retesting at 12 weeks gives the immune system enough time to respond.

False positives are a real concern, especially for HSV-2. The most commonly used commercial test (HerpeSelect) correctly identifies people who do not have HSV-2 about 96% to 97% of the time. In a population where true HSV-2 prevalence is around 12%, that accuracy gap means a meaningful fraction of low-positive results are false. The 2021 Centers for Disease Control and Prevention (CDC) sexually transmitted infections treatment guidelines specifically recommend confirmatory testing for HSV-2 index values between 1.1 and 3.5.

IgG tests also cannot tell you when you were infected or where on your body the virus lives. A positive HSV-1 IgG, for example, does not distinguish between an oral infection acquired in childhood and a genital infection acquired as an adult. Clinical history and any symptom patterns you have noticed are needed to complete the picture.

Tracking Over Time

Unlike many biomarkers, HSV IgG antibodies do not fluctuate in clinically meaningful ways once they are established. A confirmed positive result remains positive for life. The main reason to retest is after an initial negative or equivocal result when you had a recent possible exposure. In that case, retesting at 12 weeks after the exposure clarifies whether your body has produced antibodies.

If you are in an ongoing sexual relationship with a partner who has herpes and your initial test is negative, periodic retesting (every 6 to 12 months) can detect new infection early. Early detection allows you to start suppressive therapy sooner if needed and adjust prevention strategies.

What to Do with Your Results

A clearly positive HSV-2 result (index above 3.5) is reliable and warrants a conversation with a clinician about antiviral options, outbreak management, and partner disclosure strategies. Daily suppressive therapy with valacyclovir reduces HSV-2 transmission to an uninfected partner by approximately 48%, and combining suppressive therapy with condom use reduces transmission further.

A low positive HSV-2 result (index 1.1 to 3.5) should not be accepted at face value. Request confirmatory testing before making decisions based on the result. A negative result on both tests, especially if drawn more than 12 weeks after your last new sexual contact, is reassuring.

If you test positive for HSV-2 and have not been screened for HIV, that screening becomes more urgent given the established link between the two infections. A full sexually transmitted infection (STI) panel is reasonable for anyone who discovers a new HSV diagnosis, since co-infections are common.