Cytomegalovirus (CMV) is a genus of viruses in the order Herpesvirales, in the family 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. In the medical literature, most mentions of CMV without further specification refer implicitly to human CMV. Human CMV is the most studied of all cytomegaloviruses. The HCMV UL94 gene is conserved among all herpesviruses and encodes a virion protein. UL94 is a tegument protein that is expressed with true-late kinetics and localizes to the viral assembly complex during infection.