Cytomegaloviruses

Cytomegaloviruses are large herpesviruses in the genus Cytomegalovirus, within the family Herpesviridae. They have linear double-stranded DNA genomes and enveloped, icosahedral virions. Cytomegaloviruses establish lifelong latent infections after primary exposure, primarily in hematopoietic cells, and can reactivate, especially under conditions of immune suppression. Most infections in healthy individuals are asymptomatic or result in mild febrile illness.

In humans, the best known member is human cytomegalovirus (HCMV, HHV-5). Other cytomegaloviruses infect animals, including murine CMV (MCMV), rhesus CMV, guinea pig CMV, and porcine CMV; these species-specific viruses serve as important models for studying CMV biology and pathogenesis.

Transmission occurs through contact with infected bodily fluids such as urine, saliva, blood, breast milk, and semen, and can occur congenitally across the placenta. Primary CMV infection during pregnancy can result in congenital CMV, the leading infectious cause of sensorineural hearing loss and neurodevelopmental impairment in children. In immunocompromised individuals—such as organ transplant recipients and people with advanced HIV/AIDS—CMV can cause retinitis, pneumonitis, hepatitis, colitis, and encephalitis.

Diagnosis relies on serology to determine prior exposure, molecular tests (PCR) to detect viral DNA, antigenemia assays, and viral culture from urine or saliva in the early stages of infection. Treatment options include antiviral drugs such as ganciclovir and valganciclovir as first-line therapy, with cidofovir or foscarnet used for resistant or severe cases. Prophylactic or preemptive antiviral strategies are employed in high-risk transplant recipients. Vaccines against CMV are under development, but no licensed vaccine is available as of now.