Shingles is a painful condition caused by the virus (varicella-zoster virus, or VZV) that also causes chickenpox. 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. Shingles usually occurs only once in a person's lifetime. 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 July 1, 2009, issue of JAMA includes an article about shingles.