Varicella. Varicella zoster virus (VZV, also known as human herpesvirus 3) is a ubiquitous alpha-herpesvirus with a double-stranded DNA genome. VZV only naturally infects humans, with no animal reservoir; its main targets are T lymphocytes, epithelial cells and ganglia. Primary infection causes varicella (chickenpox), during which VZV becomes latent in ganglionic neurons.