Herpes Simplex Virus Infection

Definition

Herpes Simplex Virus (HSV) infection is a common viral infection caused by HSV-1 or HSV-2, resulting in recurrent vesicular lesions on the oral, genital, or other mucocutaneous sites.

Epidemiology

• HSV-1 is more commonly associated with orolabial infections, HSV-2 with genital infections
• Global prevalence: HSV-1 ~67%, HSV-2 ~11% among adults
• Higher prevalence in sexually active populations
• Transmission occurs via direct contact with infected secretions
• Asymptomatic viral shedding contributes to spread
• Recurrence is more frequent with HSV-2 genital infections
• Significant psychosocial and quality-of-life impact due to recurrent outbreaks

Etiology

• HSV-1: primarily transmitted via oral contact
• HSV-2: primarily transmitted via sexual contact
• Direct contact with vesicular fluid or mucosal surfaces
• Autoinoculation can occur in immunocompromised or naïve individuals
• Virus establishes latency in sensory nerve ganglia
• Reactivation triggered by stress, illness, trauma, or immunosuppression
• Co-factors: immunodeficiency, chronic disease, pregnancy

Pathophysiology

• Initial infection of epithelial cells leads to viral replication and vesicle formation
• Local inflammation causes pain, erythema, and ulceration
• Virus enters sensory neurons and establishes latency in dorsal root or trigeminal ganglia
• Reactivation leads to viral replication and recurrent lesions at the same dermatome
• Immune response controls severity but does not eradicate the virus
• HSV can cause systemic infection in neonates or immunocompromised individuals
• Latency-reactivation cycle contributes to recurrent disease