Subfamily: Betaherpesvirinae

Genus: Cytomegalovirus

Distinguishing features

The predicted amino acid sequences of members form a distinct lineage within the subfamily (Figure 1.Betaherpesvirinae). Most members have genomes of >200 kbp, the largest known in the family (Figure 4.Orthoherpesviridae). 

Virion

See discussion under family description. 

Genome organization and replication

Human cytomegalovirus (HCMV in the species Cytomegalovirus humanbeta5) is noteworthy for its marked genomic adaptations to cell culture, which include the disruption or loss of several genes affecting tropism in vivo (Wilkinson et al., 2015). HCMV has a high level of intraspecies diversity (Sijmons et al., 2015, Suárez et al., 2019). 

Biology

Members have primates as hosts. Infections generally result in a marked increase in cell volume (cytomegalia) and the development of prominent, distinctive nuclear and cytoplasmic inclusions. HCMV infection is usually inapparent or mild, but poses a risk to people with immature or compromised immune systems, in particular congenitally infected children, transplant recipients and people with HIV/AIDS. 

Species demarcation criteria

See discussion under family description.