What causes herpes?

Causes of Herpes

Herpes is caused by infection with herpes simplex virus (HSV), specifically HSV-1 or HSV-2, which establish lifelong latent infections with periodic reactivations throughout a person's life. 1

Types of Herpes Simplex Viruses

HSV-1

• Traditionally causes infections above the neck (orolabial herpes)
• Usually acquired through close non-sexual contact with infected persons, typically in childhood 2
• Manifests as lesions of the oro-pharynx, mouth, lips, and chin
• Can occasionally affect the eyes
• Increasingly causing genital herpes through oro-genital sexual practices 2, 1

HSV-2

• Primarily causes infections below the waist (genital herpes)
• Usually acquired through sexual contact with infected persons later in life 2
• Almost always associated with genital disease 2
• Establishes latent infection in the sacral ganglia 1

Transmission Mechanisms

• Direct contact transmission: The virus is spread through direct contact with infected lesions or body fluids
• Sexual transmission: HSV-2 is primarily transmitted through sexual contact 2
• Oro-genital practices: HSV-1 can cause genital herpes through oro-genital sexual contact 2, 3
• Asymptomatic shedding: Many infected individuals are unaware they have the virus and can transmit it even without visible symptoms 1

Infection Process

1. Primary infection: Occurs when a person without antibodies against HSV acquires the virus for the first time 1

   • Incubation period: 2-10 days (can extend up to 4 weeks) 2, 1
   • Usually the most severe manifestation of infection 2

2. Latency establishment: After primary infection, the virus establishes latency

   • HSV-1 typically persists in cervical ganglia 2
   • HSV-2 typically establishes in sacral ganglia 2, 1

3. Recurrent infections: Periodic reactivation of the latent virus 2

   • Triggered by various factors including psychological stress, menstruation, fever, local trauma, and immunosuppression 1
   • UV radiation can trigger HSV-1 reactivation 1

Epidemiology

• Herpes simplex virus infections are among the most frequently encountered human infections 4
• HSV-2 prevalence in the general population ranges from 10% to 60% worldwide 5
• In the United States, HSV-2 seroprevalence has shown a decreasing trend, from 21.0% in 1988-1994 to 17.0% in 1999-2004 6
• HSV-1 seroprevalence has also decreased from 62.0% to 57.7% during the same period 6
• HSV-1 now accounts for about half of new genital herpes cases in developed countries 5

Clinical Implications

• Genital herpes is the main cause of genital ulcers worldwide 5
• Most genital HSV-2 infections are unrecognized and undiagnosed 5
• HSV-2 infection increases the risk of HIV acquisition by approximately three times 5
• Neonatal herpes is an uncommon but serious complication of genital herpes 5
• Recurrent genital herpes can significantly impact quality of life due to unpredictable recurrences, concerns about transmission, and potential stigma 1

Key Points for Diagnosis

• Clinical diagnosis alone is neither sensitive nor specific 5
• Laboratory confirmation is recommended for accurate diagnosis 1
• Diagnostic methods include viral culture, HSV DNA PCR, antigen detection for active lesions, and type-specific serologic testing when no lesions are present 1, 5