Human cytomegalovirus

Virus of the family Herpesviridae

Human cytomegalovirus (HCMV), also known as human herpesvirus 5 (HHV-5), is a member of the Herpesviridae family of viruses. It is a common virus that infects people of all ages and is often asymptomatic in healthy individuals. However, it can cause significant disease in immunocompromised individuals and is a major cause of congenital infections.

Virology

Cytomegalovirus virion

HCMV is a large, enveloped virus with a double-stranded DNA genome. It is classified as a betaherpesvirus, which is characterized by a slow replication cycle and the ability to establish lifelong latency in the host. The virus can reactivate from latency, particularly in individuals with weakened immune systems.

The HCMV genome is approximately 230 kilobase pairs in length and encodes for a variety of proteins that help the virus evade the host immune response and establish infection.

Pathogenesis

HCMV is transmitted through bodily fluids such as saliva, urine, blood, and breast milk. Once inside the host, the virus can infect a wide range of cell types, including epithelial cells, endothelial cells, fibroblasts, and leukocytes.

In healthy individuals, HCMV infection is usually asymptomatic or may cause mild flu-like symptoms. However, in immunocompromised individuals, such as those with HIV/AIDS, organ transplant recipients, or patients undergoing chemotherapy, HCMV can cause severe disease, including pneumonia, retinitis, and gastrointestinal disease.

Congenital Infection

CMV placentitis

HCMV is the most common cause of congenital viral infection, affecting approximately 0.5% to 2% of all live births. Congenital HCMV infection can lead to a range of outcomes, from asymptomatic infection to severe disease with long-term sequelae such as hearing loss, developmental delay, and microcephaly.

The risk of congenital infection is highest when a primary maternal infection occurs during pregnancy. The virus can cross the placenta and infect the fetus, leading to placental inflammation and fetal damage.

Diagnosis

Diagnosis of HCMV infection can be achieved through serological tests that detect antibodies against the virus, as well as molecular techniques such as PCR to detect viral DNA in blood or other body fluids. In congenital infections, diagnosis may involve testing the newborn's urine or saliva for the presence of the virus.

Treatment

CMV replication cycle

Antiviral drugs such as ganciclovir, valganciclovir, foscarnet, and cidofovir are used to treat HCMV infections, particularly in immunocompromised patients. These drugs inhibit viral DNA synthesis, thereby reducing viral replication.

Antiviral drugs for HCMV

Treatment of congenital HCMV infection is more challenging, and the use of antiviral therapy in newborns is still under investigation. Early diagnosis and intervention are crucial to managing the disease and preventing long-term complications.

Prevention

Preventive measures for HCMV infection include practicing good hygiene, such as handwashing, and avoiding contact with bodily fluids from infected individuals. In healthcare settings, standard precautions should be followed to prevent nosocomial transmission.

Research is ongoing to develop a vaccine against HCMV, which could significantly reduce the incidence of congenital infections and disease in immunocompromised individuals.

Related pages

• Herpesviridae
• Congenital infection
• Immunocompromised host