Herpes zoster is an acute, localized infection caused by the varicella-zoster virus, the same virus that causes chicken pox. After a chicken pox infection, the virus remains in some of the body’s nerve cells where it lies dormant (inactive) until reactivated. The reactivated virus travels along nerve fibers towards the skin, multiplies and causes a painful, blistering rash. Herpes zoster is also known as shingles. In some cases, a painful condition, post-herpetic neuralgia (persistent pain), persists after zoster disappears.