When is herpes simplex virus type 2 transmissible?

When HSV-2 Is Transmissible

HSV-2 is transmissible at any time, including during asymptomatic periods without visible lesions, which represents the primary mode of transmission. 1

Continuous Transmission Risk

• Asymptomatic viral shedding occurs frequently even when no lesions are present, and this is the most common mechanism by which HSV-2 spreads between sexual partners. 2, 1
• HSV-2 is shed from genital surfaces on approximately 10.8% of days in untreated infected persons, even in the complete absence of symptoms or visible lesions. 1
• The virus is released nearly constantly in small amounts from neurons that terminate in the genital tract, creating ongoing transmission potential. 3
• Viral replication and shedding can occur simultaneously at multiple sites within the genital tract, making transmission possible through contact with any infected mucosal surface. 4

Periods of Highest Transmission Risk

• Transmission risk is highest when visible genital lesions or ulcers are present, as viral loads are substantially elevated during symptomatic outbreaks. 2, 1
• Prodromal symptoms (tingling, burning, or pain that precedes visible lesions by hours to days) indicate active viral replication and high transmission risk. 1
• The first 12 months after initial infection carry higher transmission risk due to more frequent asymptomatic shedding during this period. 5

Asymptomatic Shedding Patterns

• Asymptomatic shedding occurs more frequently with HSV-2 than with genital HSV-1 infection, making HSV-2 inherently more transmissible. 2, 5
• Even on daily suppressive antiviral therapy, asymptomatic viral shedding still occurs on approximately 2.9% of days, though this represents a significant reduction from untreated rates. 1
• Most HSV-2 infected persons (87%) are unaware they have the infection, meaning they unknowingly shed virus and transmit to partners during asymptomatic periods. 2

Transmission Reduction Strategies

• Daily suppressive valacyclovir 500 mg once daily in the infected partner reduces transmission to uninfected heterosexual partners by 48-50%, but does not eliminate transmission risk. 1
• Consistent condom use provides additional protection but does not cover all potentially infected genital skin and mucosal surfaces. 1
• Avoiding all sexual contact when visible lesions or prodromal symptoms are present is essential, though this alone does not prevent transmission since most occurs during asymptomatic periods. 2, 1

Critical Clinical Pitfalls

• Do not counsel patients that they are only infectious during outbreaks—this is the most dangerous misconception, as the majority of transmission occurs during asymptomatic shedding. 1
• Episodic treatment of outbreaks does not reduce transmission risk; only daily suppressive therapy has been shown to decrease transmission to partners. 1
• Even the combination of daily suppressive therapy plus consistent condom use does not eliminate transmission risk entirely. 1

Special Populations

• HSV-2 increases HIV acquisition risk 3-fold through genital tract inflammation and increased viral entry points, making prevention of HSV-2 transmission particularly important in at-risk populations. 2, 1
• Pregnant women with HSV-2 can transmit to neonates during delivery, with transmission risk of 25-44% during primary infection at delivery versus approximately 1% with recurrent infection. 5