The Varicella zoster virus (VZV), also known as human herpes virus 3 (HHV-3), is one of the eight herpes viruses known to affect humans (and other vertebrates). Primary VZV infection results in chickenpox (varicella), which may rarely result in complications including VZV encephalitis or pneumonia. Even when clinical symptoms of varicella have resolved, VZV remains dormant in the nervous system of the host in the trigeminal and dorsal root ganglia.