Caused by reactivation of a primary varicella-zoster virus (VZV) infection because of a decline in the virus-specific cell-mediated immunity.
Usually presents with pain described as burning or stabbing, followed by a vesicular rash in the affected dermatome.
The location of symptoms depends on the location of the affected nerve.
Diagnosis is primarily based on the typical clinical symptoms, such as dermatomal pain and eruption of grouped vesicles in the same dermatome. Confirmation can be done using polymerase chain reaction (PCR) methods.
Treatment is primarily to reduce pain using analgesics and viral replication using antiviral medicine such as aciclovir.
Antiviral therapy may reduce the severity of postherpetic neuralgia. Early antiviral therapy is particularly important in ophthalmic zoster and zoster in the immunocompromised.
Herpes zoster (HZ), caused by reactivation of varicella-zoster virus (VZV) that was acquired during a primary varicella infection, is characterised by dermatomal pain and papular rash.  The pain typically precedes the rash by several days and can persist for several months after the rash resolves. The rash usually presents in a single dermatome and typically resolves within 4 to 5 weeks. A common complication is postherpetic pain. 
Professor of Medicine and Clinical and Translational Science
University of Pittsburgh School of Medicine
KJS declares that he has no competing interests.
Dr Kenneth J. Smith would like to gratefully acknowledge Dr Linda Kalilani, a previous contributor to this monograph. LK declares that she has no competing interests.
Department of Epidemiology
Division of General Medicine and Epidemiology
UNC at Chapel Hill
JA declares that he has no competing interests.
Manchester Royal Infirmary
KM declares that he has no competing interests.
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