The spectrum of human illness caused by cytomegalovirus (CMV) is diverse and mostly dependent on the host. CMV infections in immunocompromised patients cause substantial morbidity and mortality, especially among transplant recipients and those infected with the human immunodeficiency virus (HIV). Infection in the immunocompetent host is generally asymptomatic or may present as a mononucleosis syndrome. However, occasionally, primary CMV infection can lead to severe organ-specific complications with significant morbidity and mortality. Infection of pregnant women, even if asymptomatic, is occasionally associated with the syndrome of congenital CMV in newborns.
Like other members of the Herpesvirus family, CMV establishes latent infection after the resolution of acute (or primary) infection. Productive infection leads to the synthesis of immediate-early, early, and late viral proteins. Viral deoxyribonucleic acid (DNA) has been detected in monocytes, dendritic cells, megakaryocytes, and myeloid progenitor cells in the bone marrow.
Secondary symptomatic disease may present later in the life of the host, reflecting one of two possibilities: reactivation of latent CMV or reinfection with a novel strain. Reactivation of CMV may occur at any time during a patient’s life, although the risk is higher in the setting of systemic immunosuppression, either iatrogenic or secondary to underlying medical conditions, such as the acquired immunodeficiency syndrome (AIDS).
Transmission can occur via multiple routes including sexual transmission, close contact, as in daycare centers, or blood and tissue exposure, or perinatal transmission.
Microbiology - Virology
If sample received is EDTA blood, register QCMV
CMV - PCR
CMV - Retinitis
Congenital CMV - Antenatal
Congenital CMV - Postnatal
PCR - CMV
PCR - Cytomegalovirus
CMV Retinitis: Vitreous fluid or eye aspirate - minimum volume 0.3mL
CMV encephalitis or meningitis: CSF sample minimum volume 0.5mL
Fresh tissue (in saline) is preferrable to formalin fixed tissue where available. Formalin fixed tissue will only be processed after discussion with a Microbiologist
Congenital CMV infection: Postnatal diagnosis
Urine and/or Saliva swab
All babies of mothers diagnosed with primary CMV infection during pregnancy, should have CMV testing performed at birth with a CMV PCR within the first 3 weeks of life. Testing must be performed within this window to distinguish congenital from postnatal CMV infection.
Urine minimum volume 0.5mL
Saliva swabs should be collected at a minimum of 1 hour post breastfeeding. Insert a sterile cotton or polyester swab into the baby’s mouth between the gum and cheek and swirl for several seconds. Remove the swab and place it into a tube of UTM buffer for dispatch to laboratory. CHL Herpes/Syphilis Collection packs are suitable for collection, please contact LabInfo@cdhb.health.nz for stock requests.
Congenital CMV infection: Antenatal diagnosis
Amniotic fluid - recommended after 21 weeks gestation, however will test earlier.
Foetal risk is dependent on the gestation at which maternal infection occurred, and whether it is primary infection or reactivation/ reinfection. The greatest risks are in first trimester with primary infection. Prenatal diagnosis of foetal infection is performed with CMV nucleic acid tests (generally with PCR) on an amniocentesis sample. For optimal sensitivity and specificity, the amniocentesis needs to be performed at least 8 weeks after the suspected infection and usually after 21 weeks gestation. Earlier amniotic fluid samples have a high falsely negative rate.
Chilled (2 - 8 degrees Celsius)
Place specimen in PCR bag.
Cytomegalovirus Nucleic acid extraction, qualitative PCR amplification and detection
NOTE: For EDTA blood testing see CMV VIRAL LOAD
$213.17 (Exclusive of GST)
For clinical microbiologist or microbiology registrar consultation please contact Virology.
For further guidance in congenital CMV infection please refer to the PDF link below. This 2019 guidance document (RANZCOG) "Prevention of congenital cytomegalovirus (CMV) infection" is endorsed and approved by the Royal Australian and New Zealand College of obstetricians and Gynaecologists.
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