Lecture on Herpes Simplex Viruses (HSV1 and HSV2)

Overview

• HSV1 and HSV2 primarily cause mucocutaneous diseases.
  • Mucocutaneous disease affects mucous membranes and skin.
  • Commonly affects oral cavity (usually HSV1) and genital area (usually HSV2).

Pathogenesis

1. Primary Infection

   • Virus enters through mucosal surfaces or damaged epithelium.
   • Replicates in epithelial cells causing visible lesions.
   • HSV is a neurotropic virus, favoring neurons for infection.
   • Taken up by sensory neurons and transported retrograde to sensory ganglia.
   • Latent infection established in sensory ganglia.
   • Immune system halts epithelial infection; HSV remains hidden in ganglia.

2. Reactivation and Recurrent Infection

   • Latent virus in neurons can reactivate, reasons are unclear.
   • Reactivated virus replicates and is transported anterograde to mucosal or cutaneous sites.
   • Epithelial cells become infected again, forming lesions - termed recurrent infection.
   • Tingling or pain may precede lesions, indicating reactivation.
   • Early treatment upon tingling can prevent/mitigate outbreak.

Specificities of HSV1 and HSV2

• HSV-1
  • Typically oral herpes.
  • Establishes latent infection in trigeminal ganglia.
• HSV-2
  • Typically genital herpes.
  • Prefers latent infection in sacral ganglia, which innervate genital areas.

Infection Dynamics

• Primary Infection

  • Either virus can cause primary infection at either site (oral or genital).

• Recurrent Infection Specificity

  • HSV-1 recurs usually in oral cavity.
  • HSV-2 recurs usually in genital area.

Key Points

• Understanding mucocutaneous disease pathogenesis is crucial for handling HSV.
• Ganglia involvement is critical to recurrent infections.
• Recognizing early signs of reactivation can help manage outbreaks.