CMV Flashcards
Incidence
Affected pregnancy
Baseline % of seropositive woman
0.2-2.2% of births are affected
In The US 15-45 year old woman 40-90% are seropositive
most common cause of Congential infection
Transmission
The highest likelihood of MTCT is following maternal primary infection during the first trimester.
30-40% risk of intrauterine transmission, and of the infected fetuses, around one third (~10% overall) will have some disease.
In cases of maternal reinfection with CMV or reactivation of latent infection, the risk of fetal infection is lower (1-3%) although, when fetal infection occurs, the potential for and severity of fetal morbidity is similar to cases of primary infection.
On a population-basis, the majority of the health burden of congenital CMV is attributable to non-primary maternal infection, as the seropositivity (and hence latent infection) rate of the child bearing Australian population is 40-60%. -any public health strategy should also address nonprimary infection as well
How does one get CMV
Child to mother:
CMV is excreted in the saliva or urine of those with infection.
Excretion of virus, particularly at high titre, occurs more frequently in children under two, particularly children in day care.
The virus can continue to be excreted for months to years. CMV can be transmitted from urine and saliva to hands then to mucosal surfaces (e.g. mouth) or directly to the mucosal surfaces. High risk groups include parents with a child in daycare (23% risk of seroconversion per year if they have children who are shedding CMV)
Parental excretion of CMV occurs from the cervix, in semen, and in other bodily fluids.
What delayed fetal risks are there (Post natally)
The consequences of CMV infection may be present in utero or at birth. Most (90%) babies who are infected with CMV before birth are healthy at birth and have normal development. However 10-15% of all infected infants who are healthy at birth may still develop health problems in later childhood.
Prevention
All pregnant women and women trying to conceive, regardless of their CMV serology status. should be given information about CMV prevention as part of routine antenatal or prepregnancy care.
Advice:
Do not share food drinks, or utensils used by children (under the age of 3 years) Do not put a child’s dummy / soother in your mouth Avoid contact with saliva when kissing a child (“kiss on the forehead not on the lips”) Thoroughly wash your hands with soap and water for 15-20 seconds especially after changing nappies or feeding a young child or wiping a young child’s nose or saliva Clean toys, countertops and other surfaces that come into contact with children’s urine or saliva
Serological screening for CMV
is it indicated?
Universal routine serological screening for CMV in pregnancy is not recommended.
Pre-pregnancy or early pregnancy screening with CMV IgG may be considered for women who are high risk of infection. Early determination of CMV serostatus may aid in distinguishing between primary infection and reactivation/reinfection during pregnancy if clinically indicated, but does not remove the need to follow recommended hygiene measures.
Clinical work up in a mother
Women with suspected CMV infection in pregnancy should have CMV serology testing for IgG and IgM, and IgG avidity if CMV IgG and IgM are positive.
Diagnosis of primary CMV is based upon: new IgG or IgM with negative / low avidity IgG
Interpretation of CMV serology can be difficult as the IgM response may last up for 16 weeks post infection, may reappear with reactivation or reinfection and false positives occur due to cross reaction with other viruses.
CMV IgG avidity is more useful for timing maternal infection if primary infection during pregnancy is suspected.
A low CMV IgG avidity is suggestive of recent infection (3 months ago; Intermediate avidity – is not informative for assessing timing of infection. The IgG avidity testing is now standard and comparable within a laboratory, although differences in the avidity index depend on the kit/ technique the laboratory used and serial results from different laboratories should be compared with caution.
Can compare to booking bloods
Maternal presentation
The majority of women with acute CMV infection have no symptoms. However, serological and virological testing for CMV should be considered if a woman presents with flu-like illness, malaise, fever, and lymphadenopathy, or if fetal signs of CMV have been detected on ultrasound (i.e. case-finding, rather than screening)
Fetal / neonatal risks
Baby gets sick after birth quickly
Fetal and newborn manifestations of congenital CMV include growth restriction, microcephaly, cerebral ventriculomegaly, intracerebral calcifications, ascites/hydrops, hepatosplenomegaly, chorioretinitis, thrombocytopenia, anaemia, stillbirth and neonatal death.
Also ‘ blueberry muffin rash’
Long term sequelae that may not be evident until later childhood include sensorineural hearing loss, delayed psychomotor development, cerebral palsy, and visual impairment.
Fetal work up if acute maternal infection
Refer MFM Prenatal diagnosis of fetal infection is performed with CMV nucleic acid tests (generally with PCR) on an amniocentesis sample - >8 weeks after the suspected infection and usually >21 weeks gestation (if early high false negative rat)
Serial ultrasound surveillance +/- MRI are recommended when CMV is proven on amniocentesis to monitor for fetal growth restriction and structural abnormalities, in particular brain abnormalities.
When both ultrasound and MRI are normal, the prognosis is generally good.
All babies of mothers diagnosed with primary CMV infection during pregnancy, should have CMV testing performed with a CMV PCR of saliva or urine with the first 3 weeks of life.
Fetal infection - management
If an infant is diagnosed with congenital CMV, discussion with a paediatrician / ID
Congential CMV needs Long term follow up of hearing is recommended
Testing for congenital CMV should be considered for infants that have an abnormal newborn hearing screen result.
Breastfeeding should be encouraged. There is no evidence to suggest that postnatal CMV transmission during breastfeeding has any adverse effects on healthy infants.
Fetal Ix
MRI and CMV in urine
MRI - periventricular calcifications
Ganciclovir reduced the progression to deafness (oes not stop cognitive effects)
Treatment
No vaccine or treatment
