Betaherpesvirinae establish latency (site where virus lies dormant until reactivated) in leukocytes. This is different from Alphaherpesvirinae, which establish latency in neurons, and Gammaherpesvirinae, which establish latency in cells of the immune system, such as B-cells.
There are four known member species of the Betaherpesvirinae subfamily that are infectious for humans:
- Human cytomegalovirus (HCMV), also known as human herpesvirus 5 (HHV-5),
- Human herpesvirus 6A and 6B (HHV-6A and HHV-6B), which were classified as distinct species in 2012,
- Human herpesvirus 7 (HHV-7)
Human cytomegalovirus (HCMV, HHV-5) "seems to have a large impact on immune parameters in later life and may contribute to increased morbidity and eventual mortality." Human herpesvirus 6A (HHV-6A) has been described as more neurovirulent, and as such is more frequently found in patients with neuroinflammatory diseases such as multiple sclerosis. Both human herpesvirus 6B (HHV-6B) and human herpesvirus 7 (HHV-7), as well as other viruses, can cause a skin condition in infants known as exanthema subitum, roseola infantum (rose rash of infants) or the sixth disease.
The Herpesviridae Study Group has proposed that the subfamily Betaherpesvirinae be divided into the following four genera:
- Cytomegalovirus
- Muromegalovirus
- Roseolovirus
- Proboscivirus