infectious diseases
Herpes Zoster
Introduction
Herpes zoster is infection that results when varicella-zoster virus reactivates from its latent state in a posterior dorsal root ganglion. Symptoms usually begin with pain along the affected dermatome, followed within 2 to 3 days by a vesicular eruption that is usually diagnostic. Treatment is with antiviral medications, ideally given within 72 hours after skin lesions appear. (See Overview of Herpesvirus Infections .) Chickenpox and herpes zoster are caused by the varicella-zoster virus (human herpesvirus type 3); chickenpox is the acute, primary infection phase of the virus, and herpes zoster (shingles) represents reactivation of virus from the latent phase. Herpes zoster inflames the sensory root ganglia, the skin of the associated dermatome, and sometimes the posterior and anterior horns of the gray matter, meninges, and dorsal and ventral roots. Herpes zoster frequently occurs in older adults and people living with HIV and is more frequent and severe in patients who are immunocompromised because cell-mediated immunity in these patients is decreased. There are no clear-cut precipitants. 