Herpes Zoster and Post Herpetic Neuralgia

Herpes zoster ‘shingles’ is the clinical manifestation of the reactivation of a life long latent varicella zoster virus from dorsal root or cranial nerve ganglia, normally contracted after a chickenpox infection ‘varicella’ in early life.  After the primary infection the virus is possibly frequently reactivated, but competent cell mediated immunity prevents clinical manifestation.

These asymptomatic reactivation and contact with people infected with chicken pox may enhance the immunity.  The commonest cause of viral recurrence is decline in cell-mediated immunity related to age.  Reduced immunity associated with some malignancies, chemotherapy, radiotherapy, HIV, and immunosuppressant drugs are also risk factors.