Varicella zoster virus (VZV) is one of eight herpesviruses known to infect humans. VZV infections are species-specific to humans. It causes chickenpox (varicella), a disease most commonly affecting children, teens and young adults and herpes zoster (shingles) in older adults; shingles is rare in children. VZV is known by many names, including chickenpox virus, varicella virus, zoster virus, and human herpesvirus type 3 (HHV-3).