They are large icosohedral nucleocapsids with an outer envelope consisting of the lipid bilayer membrane from the infected cell. Their genome is dsDNA 124-230kb. They cause lifelong latent infections of the host. Once latency is established, frequency of reactivation depends on multiple factors including virus subfamily and host physiology.
- Clearance (no virus present, no viral nucleic acid)
- Persistence (low level of virus from small percentage of cells)
- Latency (no virus present, viral nucleic acid in some tissues)
- Virus remains latent
- Virus is shed asymptomatically
- Virus is reactivated, causing symptoms
There are 8 herpesviruses which infect humans:
| Virus | Subfamily | Disease | State of Latency |
| Herpes Simplex Virus I | α | Orofacial lesions | Sensory nerve ganglia |
|---|---|---|---|
| Herpes Simplex Virus II | α | Genital lesions | Sensory nerve ganglia |
| Varicella Zoster Virus | α | Chicken Pox (recurs as shingles) | Sensory nerve ganglia |
| Cytomegalovirus | β | Microcephaly | Lymphocytes |
| Espstein-Barr Virus | γ | Infectious Mononucleosis | B lymphocytes & salivary glands |
| Human Herpesvirus 6 | γ | Roseola Infantum | CD4 T Cells |
| Human Herpesvirus 7 | γ | Roseola Infantum | CD4 T Cells |
| Human Herpesvirus 8 | γ | Kaposi’s Sarcoma | Kaposi’s Sarcoma Tissue |
HSV1 and HSV2 are transmitted by skin to skin contact. It does not penetrate intact skin, but rather requires mild abrasion or chapping of skin. HSV1 causes 95% of orofacial herpes (remainder are HSV-2, but seldom recurs there) & causes 10-30% of primary genital herpes. HSV2 causes primary and recurrent genital infections & may cause primary oral herpes, but like HSV-1 it seldom recurs outside its area of tropism.
| Viral Culture | A direct comparison. |
|---|---|
| Monoclonal Antibody | Usage of a monoclonal antibody on a specimen. |
| PCR | Virus-specific and fast, used when a diagnosis must be made quickly. |