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HerpesvirusesComments

Herpesviruses

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:

VirusSubfamilyDiseaseState of Latency
Herpes Simplex Virus IαOrofacial lesionsSensory nerve ganglia
Herpes Simplex Virus IIαGenital lesionsSensory nerve ganglia
Varicella Zoster VirusαChicken Pox (recurs as shingles)Sensory nerve ganglia
CytomegalovirusβMicrocephalyLymphocytes
Espstein-Barr VirusγInfectious MononucleosisB lymphocytes & salivary glands
Human Herpesvirus 6γRoseola InfantumCD4 T Cells
Human Herpesvirus 7γRoseola InfantumCD4 T Cells
Human Herpesvirus 8γKaposi's SarcomaKaposi'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.

Diagnosing a Herpesirus Infection

Viral CultureA direct comparison.
Monoclonal AntibodyUsage of a monoclonal antibody on a specimen.
PCRVirus-specific and fast, used when a diagnosis must be made quickly.