Cytomegalovirus (CMV) (from the Greek cyto-, "cell", and megalo-, "large") is a genus of viruses in the order Herpesvirales, in the family (150-200nm in diameter [hiv virus 120nm]) Herpesviridae, in the subfamily Betaherpesvirinae. Humans and monkeys serve as natural hosts. There are currently eight species in this genus including the type species, human cytomegalovirus (HCMV, human herpesvirus 5, HHV-5), which is the species that infects humans. Diseases associated with HHV-5 include glandular fever, and pneumonia.