Shingles is a painful condition caused by the virus that also causes chickenpox (varicella-zoster virus, or VZV). It affects about 1 million individuals per year in the United States alone. Shingles, also known as herpes zoster, occurs in persons who have already had chickenpox. Most individuals who develop shingles are older than 50 years, have other medical problems (such as cancer), or are immune-suppressed from medications they take (such as steroid medications). The virus (VZV) causing shingles and chickenpox is a type of herpes virus. It is a different herpes virus from the ones responsible for cold sores or for genital herpes. VZV remains in nerve tissue after a person recovers from chickenpox. The virus remains dormant (inactive) until reactivated to cause shingles. The cause of this reactivation is not completely understood. The January 12, 2011, issue of JAMA includes an article about shingles. This Patient Page is based on one previously published in the July 1, 2009, issue of JAMA.