What is shingles and what cause it?

Varicella virus: Shingles is a reactivation of the chicken pox virus (varicella). After chicken pox the virus may remain in a dormant state and reactivate year later. It causes a painful blistering rash. You should see your doctor immediately if you get it because treatment is most effective if started within 48 hours after the rash appears.

Only varicella virus: Shingles is a condition where the zoster virus emerges from hibernation in one of your nerve roots. It travels down the nerve and exits in the distribution of that nerve where it causes pain, blisters and skin sensitivity. The only way you get shingles is to have had chickenpox in the past or have received the vaccine (although less often).