
Affecting an estimated one million Americans each year, herpes zoster (shingles) is caused by the same virus that causes chickenpox: the varicella-zoster virus. After an initial infection with chickenpox (varicella), the virus lies dormant in the dorsal root or cranial sensory ganglia; however, the virus can reactivate later in life, causing shingles. Shingles is estimated to affect one in every five persons during their lifetime. The frequency and severity of the infectious disease increase with advancing age.