The Collaborative International Dictionary of English v.0.48:

Herpesvirus \Her"pes*vir`us\, n. (Med.)
   any of several dozen DNA-containing virus of the family
   Herpetoviridae, including among them such
   human-disease-causing agents as Herpes simplex virus
   causing oral and genital herpes, varicella-zoster virus
   (Herpes zoster virus) causing shingles and chickenpox
   (varicella), Epstein-Barr virus (EB virus) causing
   infectious mononucleosis, and Cytomegalovirus.
   [PJC]

WordNet (r) 3.0 (2006):

cytomegalovirus
    n 1: any of a group of herpes viruses that enlarge epithelial
         cells and can cause birth defects; can affect humans with
         impaired immunological systems [syn: cytomegalovirus,
         CMV]