Shingles occurs in people who have had chickenpox and is a reactivation of the dormant virus.
Shingles often occurs many years after the initial chicken pox infection.
Shingles is contagious and may itself cause chickenpox. However, contact with a person with shingles or chickenpox cannot cause shingles. After the chickenpox virus has been contracted, it travels from the skin along the nerve paths to the roots of the nerves where it becomes inactive. When the virus is reactivated, it travels via the nerve paths to the skin. It is not known what factors trigger a reactivation of the virus.