Shingles is a disease caused by the varicella-zoster virus, the same virus that causes chickenpox. After an attack of chickenpox, the virus lies dormant in certain nerve tissue. As people age, it is possible for the virus to reappear in the form of shingles, which is estimated to affect 2 in every 10 people in their lifetime. Shingles is characterized by clusters of blisters, which develop on one side of the body and can cause severe pain that may last for weeks, months or years after the virus reappears.