Varicella-Zoster virus (VZV) is a human herpes DNA virus, type 3. The virus is transmitted by aerosols, is a highly contagious, infects mucous membranes, skin and neurons and causes chicken pox (Varicella). Recurrent infection resulting from reactivation of virus incorporated in the genome of satellite cells surrounding dorsal root ganglia causes shingles (Zoster). The chickenpox rash occurs two weeks after respiratory infection with the virus and is characterized by the classic dermatologic finding of macules, which progress to vesicles resembling "a dew drop on a rose petal." Primary and recurrent infection is generally self-limited.

Anti-viral treatment of VZV is indicated in immunocompromised patients and pregnant women in their third trimester. Therapy is also instituted if VZV pneumonitis, corneal or trigeminal ganglion involvement is present in immunocompetent individuals. Encephalitis is an infrequent complication.