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Microbiology · Human herpesviruses

Cytomegalovirus !

  • Virus
  • Enveloped
  • Exam priority: medium

A very common virus that usually goes unnoticed but is the main congenital infection and causes severe disease in the immunocompromised.

Updated 2026-11-01

Also called: CMV, HHV-5

At a glance

Shape
Icosahedral with tegument and envelope
Genome
Linear double-stranded DNA
Envelope
Enveloped
Family
Herpesviridae (betaherpesvirus)
Size
The human herpesvirus with the largest genome

Morphology

  • Very large infected cells (cytomegaly)
  • Owl's eye intranuclear inclusions on biopsy

Transmission

  • Saliva, urine, genital secretions and breast milk
  • Across the placenta and at birth
  • Organ transplantation and transfusion
  • Contact with young children who shed the virus

Reservoir: Humans

Isolation precautions

What the care team adds to standard precautions.

  • Standard

Virulence factors

  • Latency in monocytes and other myeloid cells
  • Reactivation when cell-mediated immunity fails (AIDS, transplantation)
  • Viral proteins that reduce antigen presentation to T cells

Diseases it causes

Clinical picture

  • Most infected newborns have no signs at birth
  • Symptomatic congenital CMV: petechiae, jaundice, hepatosplenomegaly, microcephaly, periventricular calcifications, chorioretinitis
  • Sensorineural hearing loss may appear or progress after the newborn hearing screen
  • Fetal transmission is more likely with maternal primary infection, although most cases come from mothers infected before pregnancy

Diagnosis

  • Newborn: PCR on saliva (confirmed on urine) within the first 2 to 3 weeks of life
  • After 3 weeks, congenital and acquired infection can no longer be told apart
  • IgM and IgG cannot diagnose congenital CMV
  • In the immunocompromised: PCR viral load, eye examination and biopsy with owl's eye inclusions

Treatment

Ganciclovir or valganciclovir (activated by the viral UL97 kinase) for severe disease and for the symptomatic newborn; foscarnet or cidofovir for resistance. Ganciclovir can cause bone marrow suppression.

Drug class only; doses and regimens are set by the clinician from the current guideline.

In Pharmacology:

Prevention

  • Hand hygiene after nappy changes or contact with young children's saliva, especially in pregnancy
  • Leukoreduced or seronegative-donor blood for vulnerable recipients
  • Prophylaxis or PCR monitoring in transplant recipients
  • Standard precautions (also for newborns and the immunocompromised)

Test yourself

Think of the answer, then tap the question to see it.

Which sample and time window confirm congenital CMV?

PCR on saliva (confirmed on urine) within the first 2 to 3 weeks of life.

Which eye disease does CMV cause in advanced AIDS?

CMV retinitis, which can lead to blindness without treatment.

Which isolation precautions does a newborn with congenital CMV need?

Standard precautions only, with good hand hygiene, especially for pregnant staff.

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← Back to the group: Human herpesviruses

Educational content on microorganisms; not a treatment guide and no substitute for a health professional's advice. No doses are given.

Sources: Clinical Overview of CMV and Congenital CMV (CDC, 2024); CMV retinitis (MedlinePlus (NLM), 2024); Appendix A: Type and Duration of Precautions Recommended for Selected Infections and Conditions (CDC, 2024).

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Representative model, for educational purposes only.