Types of Herpes Viruses
There are eight distinct types of human herpes viruses (HHV), organized into three subfamilies: alpha (HSV-1, HSV-2, and VZV), beta (HCMV, HHV-6, and HHV-7), and gamma (EBV and KSHV). 1, 2
The Eight Human Herpes Viruses
Alpha Subfamily
- Herpes Simplex Virus Type 1 (HSV-1): Primarily causes orolabial disease (cold sores), though increasingly causes genital herpes through oro-genital contact 3
- Herpes Simplex Virus Type 2 (HSV-2): Nearly exclusively causes genital disease and is almost always sexually transmitted 3
- Varicella-Zoster Virus (VZV): Causes chickenpox (primary infection) and shingles (reactivation) 1, 2
Beta Subfamily
- Human Cytomegalovirus (HCMV): A common infection that can cause severe disease in immunocompromised patients and neonates 1, 2
- Human Herpes Virus-6 (HHV-6): Causes roseola infantum in children 1, 2
- Human Herpes Virus-7 (HHV-7): Also associated with childhood febrile illnesses 1, 2
Gamma Subfamily
- Epstein-Barr Virus (EBV): Causes infectious mononucleosis and is associated with certain malignancies 1, 2
- Kaposi's Sarcoma-Associated Herpesvirus (KSHV/HHV-8): Associated with Kaposi's sarcoma, particularly in immunocompromised patients 1, 2
Key Clinical Distinctions for HSV-1 and HSV-2
Traditional Anatomical Distribution
- HSV-1 traditionally manifests above the neck, acquired through close contact (usually in childhood), affecting the oro-pharynx, mouth, lips, chin, and occasionally eyes 3
- HSV-2 traditionally manifests below the waist, acquired through sexual contact later in life, affecting genital mucosa, genital skin, and perigenital regions 3
Important Clinical Caveat
The anatomical distinction between HSV-1 and HSV-2 is not absolute—genital herpes is frequently caused by HSV-1 due to oro-genital sexual practices, and HSV-1 has become an increasing cause of first-episode genital herpes in well-resourced settings. 3 The lesions and natural history of infections caused by either type are very similar 3
Epidemiological Context
Prevalence Data
- In the United States (2015-2016), 47.8% of the population aged 14-49 years is seropositive for HSV-1 and 12.1% for HSV-2 3
- More than 90% of adults worldwide are infected by one or multiple human herpes viruses 2
- HSV-1 seroprevalence reflects both oral and genital infection 3
Universal Characteristic
All eight human herpes viruses establish latent infection in the host and can undergo lytic reactivation under certain pathophysiological conditions 2. This means that while antiviral agents can control symptoms and prevent outbreaks, they cannot cure these infections 1.