Varicella zoster virus (VZV) is one of eight herpes viruses known to infect humans and other vertebrates. VZV commonly causes chicken-pox in children and both shingles and postherpetic neuralgia in adults. Primary VZV infection results in chickenpox, which may rarely result in complications including encephalitis or pneumonia. VZV, like other herpes viruses, remains dormant in the nervous system of the infected person, and in 10-20% of cases the VZV reactivates later in life producing a disease known as herpes zoster or shingles. Serious complications of shingles include postherpetic neuralgia, zoster multiplex, myelitis, herpes ophthalmicus, or zoster sine herpete.