Classification and Structure



There are several different types of mammalian CMV, including those within many different monkey species. However, CMV found in animals has been shown to differ in genomic structure and is believed to not be transmittable to humans.

CMV, a double-stranded DNA virus, belongs to the Herpesviridae (Herpesvirus) family. This family includes herpes simplex virus type 1 and type 2, varicella zoster virus, human herpes virus 6, 7, and 8, and Epstein-Barr virus. Out of the entire family of Herpesviruses, CMV has the largest genome (230 kbp). Human CMV can only reproduce inside human host cells, and has most successful reproduction using human fibroblasts as hosts.

Classification Systems


There are several different classification systems, but the two main systems are the International Committee on Taxonomy of Viruses (ICTV) classification and the Baltimore classification.

ICTV Classification

The ICTV classification categorizes viruses into an order, family, subfamily, genus, and species, much like cellular organisms are classified. The six orders that have been established so far include the Caudovirales, Herpesvirales, Mononegavirales, Nidovirales, Picornavirales, and Tymovirales. CMV belongs to the Herpesvirales order, which includes other dsDNA (double-stranded DNA) viruses.

Baltimore Classification

The Baltimore classification categorizes viruses according to their nucleic acid type (RNA or DNA), strandedness, sense (comparable polarity), and method of replication.
Group I - dsDNA viruses*
Group II - ssDNA viruses
Group III - dsRNA viruses
Group IV - positive sense ssRNA viruses
Group V - negative sense ssRNA viruses
Group VI - ssRNA, reverse transcriptase viruses
Group VII - dsDNA, reverse transcriptase viruses

*The Herpesviruses, including CMV, are classified in this group.