Betaherpesvirinae

Betaherpesvirinae is a subfamily of the Herpesviridae family within the order Herpesvirales. It comprises three genera: Cytomegalovirus, Muromegalovirus, and Roseolovirus. Betaherpesviruses are characterized by large double-stranded DNA genomes, enveloped icosahedral virions, a relatively slow replication cycle, and a propensity to establish latency in hematopoietic cells.

In humans, the most clinically important member of Betaherpesvirinae is human cytomegalovirus (HCMV, HHV-5) of the genus Cytomegalovirus. The Roseolovirus genus includes human betaherpesvirus 6A, 6B, and 7 (HHV-6A, HHV-6B, HHV-7). The Muromegalovirus genus contains murine cytomegalovirus (MCMV), used as a model for human infection.

Biology and latency: Betaherpesviruses infect a broad range of vertebrates, but display narrow host range in vivo. They establish lifelong latency primarily in hematopoietic cells, with reactivation under immunosuppression or stress. Tropism often includes monocytes, macrophages, glandular and lymphoid tissues.

Clinical relevance: In healthy individuals, infections are often asymptomatic or mild. Human cytomegalovirus (HHV-5) can cause congenital disease with sensorineural hearing loss and neurodevelopmental impairment; reactivation in immunocompromised hosts can cause retinitis, pneumonitis, or colitis. Roseoloviruses (HHV-6A/B, HHV-7) cause roseola infantum in young children.

Diagnosis and treatment: Detection relies on serology, antigen detection, and PCR for viral DNA in blood or tissues. Management includes antiviral agents such as ganciclovir or valganciclovir; foscarnet or cidofovir in resistant cases. Vaccines are not widely available; prevention focuses on infection control and maternal screening in high-risk settings.