Herpes Zoster, also known as shingles or zoster, is a viral infection caused by the same virus that causes chicken pox. Anyone who has had chicken pox can develop herpes zoster. The virus remains dormant to inactive in certain nerve root cells of the body and only when it reactivates does zoster occur. About 20 percent of those people who have had chicken pox will get zoster at some time during their lives. Fortunately, most people will get zoster only once.