Postnatal cytomegalovirus (HCMV) infection is well characterized in
preterm infants, where it can lead to severe symptomatic infection. We
analyzed the rate and route of transmission of postnatal HCMV infections
in full-term babies during the first year of life. A cohort of 120 HCMV
seropositive mothers and their 122 newborns were tested after delivery
for HCMV DNA shedding in different bodily fluids. Postnatal HCMV
infection was defined as the detection of >2.5×10
2 HCMV-DNA copies/mL in infants’ saliva swabs.
Maternal neutralizing antibody serum titer, HCMV specific T-cell
response, and HCMV glycoprotein B (gB) IgG on breastmilk were analyzed.
HCMV shedding was detected in 67 of 120 mothers (55.8%), and 20 of 122
infants (16.4%) developed HCMV infection within the first three months
of life. Six additional infants were infected during the first year, for
a postnatal infection rate of 21.3%. Viral shedding was more frequent
in breastmilk than saliva, urine and vaginal secretions, and the mothers
of infected infants showed higher levels of HCMV-DNA in milk. No
association was found between the antibody levels in serum or milk and
maternal viral shedding, whereas a slightly lower frequency of
HCMV-specific CD4 + T-cells with long-term memory
phenotype was observed in women with HCM-DNA-positive milk. About one
out of five infants develop HCMV infection within the first year of
life. Breastmilk appears the major route of transmission of the
infection, maternal saliva have a minor role whereas the role of vaginal
secretions is negligible.