What testing is recommended for a person with possible herpes simplex virus exposure?

Recommended Testing for Herpes Simplex Virus Exposure

Direct Answer

If you have active genital lesions, obtain nucleic acid amplification testing (NAAT/PCR) with HSV typing directly from the lesion—this is the gold standard with >90% sensitivity and specificity. 1 If no lesions are present, use type-specific HSV-2 serology based on glycoprotein G, but only if exposure occurred more than 12 weeks ago and you fall into a high-risk category. 1

Testing Algorithm Based on Clinical Presentation

When Active Genital Lesions Are Present

• First-line test: NAAT/PCR with HSV typing directly from the lesion, which delivers >90% sensitivity and specificity and significantly outperforms viral culture 1
• Specimen collection technique: Open vesicles with a sterile needle, collect vesicular fluid using a cotton-wool or Dacron swab (avoid calcium-alginate swabs), and vigorously swab the lesion base to obtain epithelial cells 1
• Timing matters: Collect specimens as early as possible; vesicular lesions provide significantly higher positivity rates than ulcerative or crusted lesions 1
• Always request HSV typing (HSV-1 vs HSV-2) because 12-month recurrence rates differ dramatically—approximately 90% for HSV-2 versus 55% for HSV-1 1
• If NAAT/PCR is unavailable: Viral culture may be used, but it is markedly less sensitive, especially for recurrent, ulcerative, or healing lesions 1
• If viral culture is negative yet clinical suspicion persists, follow up with type-specific HSV serology to exclude HSV-2 infection 1

When No Active Lesions Are Present

• Only appropriate test: Type-specific HSV serology based on glycoprotein G 1
• Never perform NAAT/PCR or viral culture in the absence of genital ulcers; swabs obtained without lesions are insensitive and unreliable 1
• Critical timing consideration: A negative serologic result obtained within 12 weeks of possible exposure may represent the "window period"; repeat testing after 12 weeks if recent acquisition is suspected 1

Understanding Serology Performance and Pitfalls

HSV-2 Serology Characteristics

• Overall sensitivity: 92%, but specificity varies dramatically with index value 1
• Index values 1.1–2.9: Only 39.8% specificity, meaning approximately 60% are false-positives 1
• Index values ≥3.0: Improved to 78.6% specificity, but still approximately 21% false-positives 1
• Cross-reactivity problem: Individuals with HSV-1 infection are more prone to false-positive HSV-2 serology when index values are low 1

HSV-1 Serology Characteristics

• Low sensitivity: Approximately 70%, leading to frequent false-negative results 1, 2
• Cannot distinguish oral from genital infection: HSV-1 is commonly acquired non-sexually in childhood, making it unreliable for diagnosing genital herpes 3

Interpreting Indeterminate Results

• Index values 0.9–1.1 (gray zone): Cannot definitively confirm or exclude HSV-2 infection 3
• Do not assume HSV-2 infection based solely on an indeterminate index 3
• If exposure within past 12 weeks: Repeat serologic testing after the 12-week window because antibodies may still be maturing 3
• If exposure more than 12 weeks ago: Repeat test 4–6 weeks later to determine whether the index value shifts toward a definitive result 3

Confirmatory Testing for Low-Positive Results

• All low-positive results (index 1.1–2.9) require confirmation with a second assay using a different glycoprotein G antigen 3, 2
• Confirmatory testing improves specificity from 93.2% to 98.7% and positive predictive value from 80.5% to 95.6% 2
• Western blot/immunoblot is the serologic gold standard for HSV when available 3, 2

Who Should Be Tested (High-Risk Groups)

Screening Is Appropriate For:

• Pregnant women at risk of acquiring HSV infection close to delivery 2, 4
• Men who have sex with men 2, 4
• HIV-positive persons 2, 4
• Sexual partners of individuals with known genital herpes 2, 4
• Persons at high risk for STDs who are motivated to reduce sexual risk behavior 4

Screening Is NOT Recommended For:

• Routine screening of asymptomatic adolescents and adults (USPSTF Grade D: harms outweigh benefits) 1
• Universal screening in pregnant women is unlikely to be beneficial 4
• Widespread screening in low-risk populations due to high false-positive rates 2

Critical Pitfalls to Avoid

• Do not use Tzanck smear or direct immunofluorescence assay for genital HSV diagnosis; both lack adequate sensitivity and specificity 1
• Do not order serology when active lesions are present—this misses the opportunity for definitive NAAT/PCR diagnosis 2
• Do not report low-positive results without confirmation—this leads to false-positive diagnoses with significant psychological and relationship consequences 2
• Do not test too early after exposure—allow at least 12 weeks for adequate antibody development 3
• Do not rely on clinical diagnosis alone—80–90% of genital herpes infections are subclinical, making clinical findings neither sensitive nor specific 1
• Do not use point-of-care antibody tests in low-risk populations due to high false-positive rates, especially when index values are low 1

Key Epidemiological Context

• Approximately 91% of HSV-2 seropositive persons are unaware of their infection because they never develop recognizable symptoms 1
• The majority of genital herpes transmission originates from individuals who are unaware of their infection or are asymptomatic at the time of transmission 1
• Approximately 70% of adults worldwide possess HSV-1 antibodies acquired in childhood, which increases the likelihood of false-positive HSV-2 results on commercial IgG assays 3