Herpes Testing Explained: HSV-1 and HSV-2, Windows, and Accuracy

Genital herpes is caused by two related viruses: herpes simplex virus type 1 (HSV-1) and herpes simplex virus type 2 (HSV-2). HSV-1 is also the familiar cause of cold sores around the mouth. HSV-2 has historically caused most genital herpes, though HSV-1 now causes a meaningful share of new genital infections. Either type can cause oral or genital symptoms.

Herpes spreads through skin-to-skin contact with an infected site — including contact when no sores are visible. CDC emphasizes that the virus can be shed intermittently without symptoms, which is why most transmission happens when people do not know they have it. After the initial infection, HSV establishes a lifelong presence in the body; reactivation can produce visible outbreaks or silent shedding.

Symptoms vary widely. During a first (primary) episode, some people develop blisters that become painful sores, sometimes with flu-like symptoms; others have mild symptoms easy to miss, and many never notice anything at all. CDC's summary is direct: most people with genital herpes have no or very mild symptoms and do not know they have it. Recurrent outbreaks, when they occur, are usually shorter and less severe — especially with HSV-2 — and often decrease over time. Because symptoms alone cannot distinguish HSV-1 from HSV-2, type-specific testing provides what clinical guesswork cannot.

Two testing routes exist. If an active lesion is present, a swab can be collected for viral testing (NAAT or culture), detecting the virus directly from the sore. When no lesion is present, type-specific IgG blood tests look for antibodies to HSV-1 and HSV-2 separately.

The assay matters. CDC states that only type-specific tests based on glycoprotein G (gG1 for HSV-1, gG2 for HSV-2) should be used; type-common antibody tests cannot tell the two viruses apart, and IgM testing is not recommended because it is not type-specific.

Timing matters just as much. USPSTF evidence reviews summarize that type-specific IgG antibodies typically become detectable within about 6 weeks to 3 months after infection. CDC advises repeating type-specific antibody testing about 12 weeks after a presumed recent HSV-2 exposure, because early infections can still test negative while antibodies are still developing.

Herpes blood tests carry a real accuracy caveat that both CDC and USPSTF put in writing. Type-specific gG2 tests for HSV-2 vary in sensitivity — CDC cites roughly 80% to 98% across available assays — with false negatives more likely early in infection, which is why the antibody window and the 12-week retest guidance matter.

The harder issue is false positives in lower-prevalence settings. CDC reports that the most commonly used HSV-2 enzyme immunoassay often reads falsely positive at low index values, and advises confirmatory testing with a second method before results are interpreted. USPSTF found that in general primary-care populations — where HSV-2 prevalence is relatively low — the positive predictive value of widely available tests can fall substantially; using prior estimates, USPSTF calculated that nearly half of screening diagnoses in such populations could be false. That is one reason CDC does not recommend routine herpes blood testing for people without symptoms in most situations, and why a reactive result often warrants confirmation before it is treated as settled.

None of this makes testing useless — it means testing works best when matched to the right question: confirming present lesions, evaluating a partner's known infection, or investigating atypical symptoms. Any accuracy claim should be read together with the test's window and the population it is used in.

A type-specific result clarifies which virus is involved — information that matters because genital HSV-2 tends to recur more often than genital HSV-1. For couples, knowing a partner's status shapes conversations about disclosure, whether the other partner should be tested, and shared decisions about sexual health.

There is no approved vaccine for HSV, and antiviral medications do not remove the virus from the body. What antivirals do — reliably — is manage the condition: daily suppressive therapy reduces outbreak frequency, and CDC notes that suppressive valacyclovir reduces the risk of transmitting HSV-2 to susceptible partners. Episodic therapy shortens individual outbreaks. Condoms, used consistently and correctly, can reduce — but not eliminate — transmission risk.

Genital herpes is common, manageable, and heavily stigmatized relative to its clinical reality. A factual result replaces fear with information: what to expect, what options exist, and how to talk with partners. That is the real value of testing — clarity, not catastrophe.

Herpes sits in a different data landscape than chlamydia, gonorrhea, syphilis, or HIV. CDC's nationally notifiable STI surveillance does not report herpes through systematic case counting in the same way, so city-level herpes rates are not part of standard metro surveillance tables. This site's metro dataset — covering chlamydia, gonorrhea, syphilis, and HIV — does not include herpes either, which is why this page presents only national and clinical context and no local herpes rates appear anywhere on this site.

National seroprevalence gives the broadest picture. Estimates from CDC's National Health and Nutrition Examination Survey (NHANES), as cited by USPSTF, place HSV-1 antibody prevalence at roughly 48% and HSV-2 at roughly 12% among U.S. adults ages 14 to 49, with substantial variation by age, race, and ethnicity. Because many infections are asymptomatic and never reach clinical attention, seroprevalence captures exposure far better than case reports — and it also explains why false-positive rates behave the way they do in lower-risk populations.

Because herpes is not folded into routine multi-disease STI panels the way chlamydia and gonorrhea testing is, people often choose between a focused type-specific IgG test and broader testing driven by a specific concern. STDcheck offers type-specific HSV-1 and HSV-2 IgG testing as individual options — the same category of assay CDC describes.

Insurance coverage for herpes serology varies, and many people choose self-pay lab testing for privacy and speed: ordering stays independent of an insurance claim, with results delivered through a confidential portal. If testing after a possible recent exposure, expect timing to be part of the conversation — retesting at about 12 weeks is the standard approach after a presumed recent exposure.

As with all screening, results are most useful when interpreted with a professional — low-positive HSV-2 values in particular may call for confirmatory testing. This page is educational and does not replace medical advice.

Common questions about what herpes tests can and cannot tell you.