What is the most effective strategy to prevent genital herpes simplex virus type 2 transmission from an HSV‑2‑positive individual to an HSV‑2‑negative sexual partner?

How to Prevent Partner from Getting Herpes Simplex 2

The infected partner should take valacyclovir 500 mg once daily as suppressive therapy, which reduces HSV-2 transmission to an uninfected heterosexual partner by approximately 48–50% and reduces symptomatic disease by 75%. 1, 2, 3

Daily Suppressive Antiviral Therapy (Most Critical Intervention)

Valacyclovir 500 mg orally once daily is the cornerstone of transmission prevention. This regimen:

• Reduces overall HSV-2 acquisition risk by 48–50% in heterosexual discordant couples 1, 2, 3
• Decreases symptomatic HSV-2 infection in the susceptible partner by 75% 1, 4
• Lowers asymptomatic viral shedding from 10.8% of days to only 2.9% of days 1, 5, 3
• Reduces recurrence frequency from 0.40 episodes per month to 0.11 episodes per month 2, 3

This is the only antiviral strategy proven to reduce transmission—episodic treatment during outbreaks does NOT prevent spread to partners. 1, 5

Consistent Condom Use (Additive Protection)

• Latex condoms reduce HSV-2 transmission by approximately 50% in both directions (male-to-female and female-to-male) when used consistently 6, 1
• Combining daily suppressive therapy with consistent condom use provides additive protection, though neither eliminates transmission risk entirely 1, 5
• Condoms do not cover all potentially infectious skin, so transmission can still occur even with perfect use 1

Behavioral Modifications

Avoid all sexual contact during visible lesions or prodromal symptoms (tingling, burning, itching that precedes lesions) 6, 1, 5:

• Visible vesicles and ulcers contain thousands of infectious viral particles and represent the highest-risk periods 5
• However, most HSV-2 transmission (the majority of cases) occurs during asymptomatic periods when no lesions are visible, so avoiding sex only during outbreaks is insufficient 6, 1, 5

Partner Testing and Counseling

The uninfected partner should undergo type-specific HSV-2 serologic testing before initiating sexual activity 6, 1:

• If the partner is already HSV-2 seropositive, transmission is not a concern 6
• Disclosure and testing in discordant couples has been associated with reduced transmission risk 6, 1
• Approximately 81–87% of HSV-2-infected persons are unaware of their infection, so many "uninfected" partners may already be seropositive 5, 7

Both partners require comprehensive counseling about:

• The natural history of HSV-2 infection 1, 5
• Asymptomatic viral shedding as the primary transmission mechanism 6, 1, 5
• The fact that no prevention strategy eliminates risk completely 1, 5

Special Populations and Additional Considerations

Women of childbearing age must inform obstetric providers of HSV-2 status during pregnancy to prevent neonatal herpes 1, 5

HSV-2 increases HIV acquisition risk approximately threefold, making prevention particularly important in at-risk populations 6, 1, 5, 7:

• Patients with HSV-2 should be tested for HIV 7
• HIV-infected individuals require routine type-specific HSV-2 testing 1

Common Pitfalls to Avoid

Do not rely on episodic (outbreak) treatment to reduce transmission—only daily suppressive therapy has demonstrated efficacy in preventing spread 1, 5

Do not assume avoiding sex during visible outbreaks is sufficient—the majority of transmissions occur during asymptomatic periods when viral shedding is unrecognized 6, 1, 5

Do not overlook the incubation period—after exposure, viral shedding can occur 2–10 days (up to 4 weeks) before symptoms appear in a newly infected partner 5

Algorithm for Implementation

1. Start valacyclovir 500 mg once daily immediately in the HSV-2-positive partner 1, 2, 3
2. Obtain type-specific HSV-2 serology in the uninfected partner to confirm susceptibility 6, 1
3. Counsel both partners on asymptomatic transmission risk and the limitations of all prevention methods 1, 5
4. Recommend consistent latex condom use for all sexual contact 6, 1
5. Avoid all contact during prodromal symptoms or visible lesions 6, 1, 5
6. Continue suppressive therapy indefinitely as long as transmission prevention remains a goal 1, 2