Herpes Simplex Virus - HSV

Herpes simplex virus (HSV) occurs worldwide and produces a variety of clinical manifestations, ranging from mild stomatitis to fatal disease. Herpes simplex virus type 2 (HSV-2) causes recurrent genital herpes episodes more often than herpes simplex virus type 1 (HSV-1), although HSV-1 is responsible for a growing number of genital herpes cases.

Key Points

Herpes simplex virus (HSV) infections are extremely common worldwide. The herpes simplex viruses comprise two distinct types of DNA viruses: herpes simplex virus type 1 (HSV-1) and herpes simplex virus type 2 (HSV-2). While HSV subtyping is available, typing is not required for treatment. Treatment for HSV-1 and HSV-2 infections is the same.

Indications for HSV Testing

  • Sexually transmitted infection – seronegative individuals are at risk of acquiring infection from seropositive partners
    • HSV-1
      • Usually transmitted via nonsexual route
      • An increasing proportion of genital herpes is due to HSV-1
    • HSV-2
      • Majority of persons positive for HSV-2 have not been diagnosed with genital herpes
      • Individuals with HSV-2 can have mild or unrecognized disease and may shed virus from genital area intermittently
      • HSV-2 infection increases the risk of acquiring HIV infection (refer to STDs and HIV – CDC Fact Sheet)
  • Transmission from mother to neonate
    • First-time (primary) infection of woman during pregnancy – increases the risk of transmitting virus to neonate during delivery
    • Most neonatal infections are acquired intrapartum
  • Reinfection with HSV – rare, but dormant virus can be reactivated
  • Prognostic indicator and guide for treatment in transplant patients – majority of HSV infections in transplant recipients result from reactivation of latent virus, especially during early posttransplant period and periods of severe immunosuppression
  • Central nervous system (CNS) infections
    • HSV-related meningitis – generally benign and controlled with antivirals
    • Untreated HSV-related encephalitis – >70% fatality rate
  • Antiviral susceptibility for HSV (eg, acyclovir)

HSV Typing

  • Typing is unreliable and potentially clinically insignificant in many cases due to cross-reactivity between the 2 HSV types
  • Typing may be useful epidemiologically, for patient counseling regarding disease acquisition, and for some assistance with prognosis (CDC, 2014)
  • HSV subtype does not affect choice of treatment
  • Early false negative results may occur; type-specific antibody testing may not be positive until 2-3 months postinfection
  • If pursuing subtyping, HSV-1/-2 glycoprotein G (gG) antigen serology testing is recommended
    • “Type-specific” antibody testing
    • Does not detect cross-reacting antibodies
    • Provides more accurate serological assessment of HSV-1/HSV-2
  • IgM testing – limited clinical utility; not reliable for diagnosis of genital lesions or neonatal herpes (CDC, 2014)

Laboratory Testing for HSV

HSV infection can be confirmed by direct detection of the virus, detection of antibodies to HSV, or immunohistochemical testing

Virologic Testing (Direct Detection of HSV Infection)
Test Methodology Description

NAAT (PCR) testing for viral DNA

Rapid diagnostic testing.

Preferred method for CSF testing and neonates.

May detect asymptomatic HSV shedding.

High sensitivity and specificity.

Typing is included in some reflex tests.

Viral culture

Traditional gold standard test for identifying acute HSV infection in active lesions (eg, vesicles, ulcers, inflamed mucous membranes).

Molecular testing (eg, PCR)  generally preferred

High specificity but low sensitivity, especially for recurrent and healing lesions.

High rate of false negatives – sensitivity declines rapidly as lesions begin to heal.

More often positive in primary infection (80-90%) than recurrences (30%) (CDC, 2014).

Typing is included in some reflex tests.

Antigen detection by DFA

Rapid diagnostic test with culture backup for negative DFA results.

Test may be helpful in identifying acute HSV infection in active lesions.

Molecular testing is generally preferred.

Lower sensitivity compared to PCR

Typing is not included in this testing.

Cytology

Not recommended.

CSF, cerebrospinal fluid; DFA, direct fluorescent antibody; NAAT, nucleic acid amplification test; PCR, polymerase chain reaction

Type-Specific Serology Testsa
Test Methodology Description

HSV-specific glycoprotein G2 (HSV-2) and glycoprotein G1 (HSV-1)

Glycoprotein G-based type specific test is acceptable for HSV serologic diagnosis (CDC, 2015).

May be useful for the following:

  • Recurrent genital symptoms or atypical symptoms with negative HSV PCR or culture
  • Clinical diagnosis of genital herpes without laboratory confirmation
  • Patient whose partner has genital herpes

IgG testing

Sensitivity varies; false-negative results might be more frequent at early stages of infection.

Type-specific HSV IgG antibodies may require 3-6 months to form.

Follow-up testing is required to confirm negative IgG glycoprotein result in context of positive HSV types 1 or 2 antibody results.

IgM testing

Not recommended; lacks adequate predictive value for acute infection (CDC, 2015).

aHSV-1 and -2 are closely related antigenically and high cross-reactivity exists between the 2 common antigens, which may affect the accuracy of antigen-based typing tests. Serology tests that use HSV-1 or -2 glycoprotein G (gG) antigens are considered “type-specific” antibody tests and do not detect cross-reacting antibodies. Thus, they provide a more accurate serological assessment of whether the HSV is type 1 or 2. Because glycoprotein antibodies may require up to 3 months to form, follow-up testing is recommended to confirm a negative IgG glycoprotein in the context of positive HSV-1 or -2 antibody results.

Antiviral Susceptibility Testing
Test Methodology Description

Antiviral susceptibility testing

Determine susceptibility to treatment in immunosuppressed patients (eg, patients with HIV or organ transplant).

Immunohistochemical Staining
Test Methodology Description

Immunohistochemical staining of FFPE prepared tissues/cells

Not commonly ordered.

May be considered if tissue histology is suspicious for HSV.

FFPE, formalin-fixed paraffin-embedded

Diagnosis

Indications for Testing

  • Genital or oral ulcerative or vesicular lesions
  • Central nervous system (CNS) infections
    • Unidentified encephalitis
    • Encephalitis with focal neurologic symptoms
    • Herpes simplex virus (HSV)-related meningitis
  • Corneal ulcer
  • Transmission from mother to neonate – evaluate first-time (primary) infection of woman during pregnancy
  • Prognostic indicator and guide for treatment in transplant patients – majority of HSV infections in transplant recipients result from reactivation of latent virus, especially during early posttransplant period and periods of severe immunosuppression
  • Antiviral susceptibility for HSV (eg, acyclovir, foscarnet)

Criteria for Diagnosis

Genital herpes HSV case definition (CDC, 1996)

Laboratory Testing

  • Refer to Key Points for laboratory testing options
  • CNS disease – consider multiple panel testing on cerebrospinal fluid (CSF) and serum to rule out other viral illnesses (eg, varicella-zoster virus [VZV], mumps)​

Histology

Refer to Key Points

Prognosis

  • Following active infection, HSV establishes latent infection that can be reactivated 
  • Neonates
    • Better prognosis with herpes simplex virus type 1 (HSV-1) ocular, oral, cutaneous disease
    • Less neurologic morbidity with HSV-1 encephalitis
    • More sequelae from HSV-1 disseminated disease

Differential Diagnosis

Screening

Serologic screening in asymptomatic persons not recommended (U.S. Preventive Services Task Force [USPSTF], 2016; Choosing Wisely, 2018)

Background

Epidemiology

  • Prevalence (CDC, 2014)
    • Herpes simplex virus type 1 (HSV-1) – ~60% seropositivity in U.S. adults; >90% positivity in undeveloped countries
    • Herpes simplex virus type 2 (HSV-2) – ~16% seropositivity in persons aged 14 to 49 years in the U.S.
  • Age
    • 33% of cases <20 years
    • 50% of cases >50 years
  • Sex – M<F (HSV-2)
  • Transmission
    • HSV-1
      • Predominantly oral
      • Genital herpes cases increasing
      • Vertical transmission
    • HSV-2
      • Predominantly sexually (can occur during asymptomatic periods)
      • Vertical transmission (perinatally)

Organism

  • Double-stranded DNA virus of the Herpesviridae family
    • HSV-1 – majority of nongenital HSV infections
    • HSV-2 – cause of genital infections in >80% of patients
  • Biological features unique to herpes virus
    • Latency
    • Reactivation

Clinical Presentation

  • Only 10-30% of new infections are symptomatic
  • Primary infections are usually longer in duration than reactive infections
  • HSV-2 causes recurrent genital herpes episodes more often than HSV-1
    • Genital herpes (primary and recurrent)
      • Increases risk for acquiring HIV
      • Usually presents as symptomatic and painful genital ulcer
  • Pregnancy
    • Disease has higher rate of dissemination
    • More commonly associated with visceral involvement
  • Clinical symptoms are widespread and depend on clinical site, age, and immune status of host
    • Gingivostomatitis – widespread oral ulcers with lymphadenopathy (submandibular, cervical)
    • Recurrent herpes labialis – erythematous papules and vesicles on lips
    • Keratitis – eye pain, light sensitivity, corneal dendritic ulcers (can lead to blindness)
    • Conjunctivitis – increases risk of keratitis
    • Herpes gladiatorum – vesicular skin eruptions usually in face, ears, and neck areas
    • Eczema herpeticum – dissemination of oral herpes into a previously abnormal skin area (burns, atopic dermatitis)
    • Herpes sycosis – vesiculopapular lesions in beard area
    • Herpetic whitlow – vesicular eruption located on pulp of distal phalanges of hands
    • Aseptic meningitis and recurrent meningitis (Mollaret meningitis)
      • Occurs as a complication of HSV-1 or HSV-2 primary infection
      • Seizures may be first presentation
    • Visceral herpes (esophagitis, pneumonitis, hepatitis) – more common in immunocompromised patients
    • Meningitis/encephalitis – associated with focal neurologic findings
    • Neonatal herpes – infection may be acquired in utero, intrapartum, or postnatally
    • Encephalitis
    • Congenital – microcephaly, hydrocephalus, chorioretinitis, cutaneous vesicular lesions, myocarditis, skin lesions
    • Proctitis – most common in homosexual men
    • Erythema multiforme – secondary HSV is one of the most common causes

Prevention

  • Barrier contraception and daily suppressive therapy recommended to prevent partner infection
  • Pregnant women not infected with HSV-2 should be advised to avoid intercourse during the third trimester with infected partner

ARUP Lab Tests

Preferred test for detecting herpes simplex virus (HSV) infection in cerebrospinal fluid (CSF), neonates, or when rapid diagnostic test for suspected HSV infection is necessary

Detect and genotype HSV types 1 and 2

Reflex pattern: if HSV by polymerase chain reaction (PCR) result is detected, subtyping will be added

Genotype HSV types 1 and 2

Negative result does not rule out presence of PCR inhibitors in patient specimen or test-specific nucleic acid in concentrations below level of detection by this test

Traditional gold standard test for identifying acute HSV infection in active lesions (eg, vesicles, ulcers, inflamed mucous membranes)

Molecular testing is generally preferred; refer to HSV by PCR

Detect HSV by viral culture and differentiate types 1 and 2; molecular testing generally preferred

Reflex pattern: if culture is positive for HSV, then HSV typing will be added

Rapid diagnostic test with culture backup for negative direct fluorescent antibody (DFA) results

Test may be helpful in identifying acute HSV infection in active lesions (eg, vesicles, ulcers, inflammation of mucous membranes)

Molecular testing is generally preferred; refer to HSV by PCR

Sensitivity of DFA methodology dependent on adequacy of specimen; if there are fewer than 20 cells, DFA result will be reported as "sample inadequate"

Reflex pattern: if DFA is negative or inadequate, then HSV culture will be added

Aid in the histological diagnosis of HSV

Stained and returned to client pathologist; consultation available if needed

In the absence of active lesions, this is the preferred serology test for diagnosing HSV infection

Preferred testing for HSV when recent acquisition of HSV is suspected

Because glycoprotein antibodies may require 3-6 months to form, follow-up testing is recommended to confirm a negative IgG glycoprotein result in the context of positive HSV type 1 or 2 antibody results

Refer to HSV IgG glycoprotein types 1 and 2 antibody test

Detect HSV resistance to acyclovir

Detect HSV resistance to foscarnet sodium

Related Tests

Differentiate herpes simplex virus (HSV) types 1 and 2 based on cultured virus isolates

For culture combined with typing, refer to the HSV culture reflex test

Rapid diagnostic test with culture backup that may be helpful when uncertain whether a lesion is due to varicella-zoster virus (VZV) or HSV

For suspected and/or active HSV infection, molecular testing is preferred; refer to HSV by polymerase chain reaction (PCR)

If pursuing antibody testing, refer to HSV types 1 and 2 IgG glycoprotein cerebrospinal fluid (CSF) testing

If acute HSV infection is suspected, molecular testing is preferred; refer to HSV by PCR

Not a first-line test for HSV 2 typing

Order in conjunction with HSV type 1 glycoprotein antibody test

Not a stand-alone test

Order in conjunction with HSV type 2 glycoprotein antibody test

Because glycoprotein antibodies may require 3-6 months to form, follow-up testing is recommended to confirm a negative IgG glycoprotein result in the context of positive HSV types 1 or 2 antibody results

Not a stand-alone test

Molecular testing is preferred; refer to HSV by PCR test

Not recommended for HSV testing; IgM lacks adequate predictive value for acute infection

If pursing antibody testing, preferred test is HSV types 1 and 2 IgG glycoprotein antibodies

If acute HSV infection is suspected, molecular testing is preferred; refer to HSV by PCR

Reflex pattern: if HSV 1 and/or 2 IgG is 1.10 IV or greater, then HSV 1 gG-specific IgG and HSV 2 gG-specific IgG will be added

Not recommended for HSV testing; lacks adequate predictive value for acute infection

Preferred testing is HSV by PCR

Reflex pattern: if HSV 1/2 IgG, CSF is greater than or equal to 1.10 IV, then HSV 1 gG-specific IgG, CSF and HSV 2 gG-specific IgG, CSF will be added

Not recommended for HSV testing; IgM lacks adequate predictive value for acute infection

Molecular testing is preferred 

Not recommended as a stand-alone test; refer to HSV antibody reflex test

Not recommended for HSV testing; IgM lacks adequate predictive value for acute infection

If pursuing antibody testing, refer to HSV IgG glycoprotein types 1 and 2 antibodies

If acute HSV infection is suspected, molecular testing is preferred; refer to HSV by PCR

Not recommended for diagnosing congenital infections in newborns; tests should be selected individually to target the most likely infectious agents

May be used in pregnant women to assess past exposure or immunization to toxoplasma, rubella, cytomegalovirus (CMV), and HSV

​Panel includes cytomegalovirus antibody, IgG; HSV type 1 (HSV-1) and HSV type 2 (HSV-2) antibodies, IgG; rubella antibody, IgG; and Toxoplasma gondii antibody, IgG

Not recommended for diagnosing congenital infections in newborns; tests should be selected individually to target the most likely infectious agents

Panel includes cytomegalovirus antibody, IgM; HSV-1 and HSV-2 antibodies, IgM; rubella antibody, IgM; and Toxoplasma gondii antibody, IgM

Molecular testing is preferred for patients presenting with meningitis/encephalitis; refer to PCR panel for meningitis/encephalitis

Reflex pattern: if HSV 1 and/or 2 IgG, CSF is 1.10 IV or greater, then HSV 1 G-specific IgG, CSF and HSV 2 G-specific IgG, CSF will be added

Not a preferred test; refer to relevant test for the specific pathogen suspected

Reflex pattern: if HSV 1 and/or 2 IgG is 1.10 IV or greater, then HSV 1 G-specific IgG and HSV 2 G-specific IgG will be added

For best results, specify specimen source and suspected virus on order form; molecular diagnostics are preferred for suspected invasive CMV

Generally, virus-specific testing (eg, antigen detection or molecular) is recommended

Molecular diagnostics are preferred for suspected invasive CMV

Medical Experts

Contributor

Couturier

Marc Roger Couturier, PhD, D(ABMM)
Associate Professor of Clinical Pathology, University of Utah
Medical Director, Parasitology/Fecal Testing, Infectious Disease Antigen Testing, Bacteriology, and Molecular Amplified Detection, ARUP Laboratories
Contributor
Contributor

References

Additional Resources
Resources from the ARUP Institute for Clinical and Experimental Pathology®