Herpes simplex virus (HSV), including HSV-1 and HSV-2, is one of the most widespread infections globally. While HSV-1 is historically associated with oral herpes, it is an increasing cause of genital infection, and HSV-2 is the primary cause of genital herpes. Despite its high prevalence—nearly half of U.S. adults carry HSV-1 and one in eight have HSV-2—HSV is notably absent from standard sexually transmitted disease (STD) screening panels. This exclusion is a deliberate public health strategy rooted in the limitations of current testing methods and the lack of clinical benefit for asymptomatic individuals. The decision not to screen everyone balances the risks of inaccurate results against potential psychological distress and strain on healthcare resources.
The Difference Between Diagnostic and Screening Tests
Understanding why HSV is excluded from routine testing requires distinguishing between diagnostic and screening tests. When an individual has active sores or lesions, a healthcare provider uses a diagnostic test to confirm the presence of the virus itself. This involves swabbing the lesion for a viral culture or, more commonly, a Nucleic Acid Amplification Test (NAAT), such as Polymerase Chain Reaction (PCR). PCR confirms a diagnosis by detecting the viral DNA in the active lesion.
The alternative is a screening test, typically a type-specific serologic assay (blood test). This test detects immunoglobulin G (IgG) antibodies, which the immune system creates in response to an HSV infection. A positive result only confirms past exposure and that the virus is latent in the body; it does not indicate if the infection is currently active or transmissible. Health organizations recommend against using this serology test routinely in asymptomatic people because it cannot determine the exact location of the infection (oral or genital) or when the exposure occurred.
Clinical Reasons Against Routine Screening
Major health organizations, including the Centers for Disease Control and Prevention (CDC), advise against universal screening primarily due to the clinical drawbacks of the serologic antibody test. A main concern is the low positive predictive value (PPV) of the blood test, particularly within populations that have a low overall prevalence of HSV. In these low-risk groups, the probability that a positive result is a true positive can be as low as 50%, meaning half of the positive results are actually false positives. This high rate of false-positive results can lead to considerable anxiety and unnecessary follow-up testing without a clear medical benefit.
The testing is further complicated by cross-reactivity between the two virus types. HSV-1, which often causes non-sexually transmitted cold sores, is common, and the antibodies produced against it can interfere with the HSV-2 blood test. This cross-reaction can lead to an inaccurate positive result for HSV-2, particularly with low index values, making the interpretation of the serology test difficult without confirmatory testing.
Furthermore, a positive serology result for an asymptomatic individual lacks clinical utility because the diagnosis rarely changes their medical management. Treatment for HSV is reserved for managing outbreaks or for suppressive therapy in discordant couples. Since genital herpes does not lead to serious health complications in healthy, non-pregnant adults, there is no medical necessity to identify every asymptomatic case. Research suggests that knowing one’s status does not consistently lead to changes in sexual behavior, such as increased condom use. Therefore, the medical community prioritizes testing people with symptoms, where the result directly impacts treatment and counseling.
Psychosocial and Public Health Considerations
Beyond the limitations of test accuracy, the decision to exclude routine screening is influenced by the potential psychosocial consequences of a diagnosis. Receiving a positive result for a lifelong condition, even one that is often asymptomatic, can cause substantial emotional distress, anxiety, and feelings of shame due to the social stigma surrounding herpes. This psychological harm is considered to outweigh the limited medical benefit of knowing the status, especially when the positive test result may be a false alarm.
From a public health standpoint, the resource allocation required for universal screening is not deemed a justifiable expense. Implementing a mass screening program would necessitate significant resources for testing, follow-up counseling, and managing the large volume of false-positive results. The healthcare system is not currently equipped to provide the extensive and sensitive counseling that must accompany an HSV diagnosis to mitigate the psychological impact. The limited preventative benefit of universal screening, combined with the high cost and the potential for emotional harm from inaccurate results, leads public health officials to recommend against it.
When Is Testing Recommended?
The lack of routine screening recommendations shifts the focus to targeted testing based on individual risk and clinical presentation. Testing is strongly recommended if a person is experiencing signs or symptoms that could be caused by herpes, such as blisters, sores, or atypical genital discomfort. In this scenario, a diagnostic test like PCR is used on the lesion to confirm the diagnosis.
Type-specific serologic testing is useful for asymptomatic individuals who have specific risk factors. These include:
- People whose sexual partner has a confirmed diagnosis of genital herpes.
- Individuals seeking a complete STD evaluation who have multiple sex partners.
- Individuals with HIV infection, who are at increased risk for severe HSV disease.
- Pregnant individuals, where testing may be indicated near term if a known risk or symptoms are present, to prevent neonatal transmission.