It is believed that after an initial episode of varicella, the virus persists in sensory ganglia in a quiescent state, which has yet to be fully defined. Both subclinical and clinical reactivations occur. Clinical VZV reactivation is enhanced by many factors, including increasing age, immunosuppression, and local skin injury. Attacks of herpes zoster are often preceded by pain, which may persist for several days before lesions appear. Individual attacks are usually limited to one to three dermatomes, although a few isolated skin lesions at sites distant from this area are not uncommon.
Superinfections are common, and scarring can occur.
The most common complication of herpes zoster is postherpetic neuralgia, which may be severe, particularly in the elderly. Postherpetic neuralgia may be refractory to treatment and persist for months to years. Other neurologic syndromes associated with herpes zoster include segmental myelitis, Guillain-Barr syndrome, and Ramsay Hunt syndrome. Encephalitis occurs as a complication of herpes zoster primarily in immunocompromised hosts. Herpes zoster encephalitis usually is self-limited and resolves without sequelae, although fatal cases of this disorder do occur occasionally.