Chickenpox is an infectious disease characterized by fever and a blister-like rash caused by varicella-zoster virus (VZV). A first infection with VZV causes chickenpox. After recovery from chickenpox, the virus can be dormant (inactive or latent) in a nerve root (specifically the dorsal root ganglion of a sensory nerve). Reactivation of latent infection causes herpes zoster (shingles) – a localized, painful blister-like rash, in the area supplied by that nerve. Typically shingles occurs on the trunk, or face, on either the left or right side of the body, not both sides.