A High Risk of Missing Congenital Cytomegalovirus-Associated Hearing Loss through Newborn Hearing Screening in Japan

Estimates of congenital cytomegalovirus-attributable infant mortality in high-income countries: A review

As many as 5%-10% of infants with symptomatic congenital cytomegalovirus (cCMV) disease, or 0.4%-0.8% of all liveborn infants with cCMV infection, die in early infancy in high-income countries. However, estimates are uncertain due to several potential biases that can result from data limitations and study designs. First, infants with cCMV infections who die prior to diagnosis, which usually occurs at 1-4 weeks after birth, may be excluded from both the count of deaths and the denominator of cCMV births, resulting in left truncation and immortal time biases. These 'biases' are features of the data and do not reflect bias on the part of researchers, but understanding the potential existence of threats to validity can help with interpretation of findings. Left truncation of infant deaths occurring prior to diagnosis of cCMV can result in understatement of the burden of infant deaths due to cCMV. Conversely, overestimation of infant deaths associated with symptomatic cCMV may occur in clinical case series owing to greater representation of relatively severely affected infants owing to ascertainment and referral biases. In this review, we summarise the characteristics of 26 studies that reported estimates of cCMV-associated infant deaths, including potential biases or limitations to which those estimates may have been subject. We discuss study designs whose implementation might generate improved estimates of infant deaths attributable to cCMV. More complete estimates of the overall public health impact of cCMV could inform current and future screening, prevention, and vaccine research.

Expanded targeted screening for congenital cytomegalovirus infection

An early diagnosis and intervention for congenital cytomegalovirus infection can reduce long-term disability; however, the introduction of universal neonatal screening has been controversial worldwide. The present study clarified the outcome of a targeted screening protocol for detecting congenital cytomegalovirus infection based on suggestive perinatal conditions. In addition, the positive rate was compared to those from the reported studies and the validity of the targeted screening criteria was discussed. A total of 2121 newborn infants were admitted to our hospital between October 2018 and October 2021. Cytomegalovirus DNA was examined by the isothermal nucleic acid amplification method for urine samples from newborns with any of the following: microcephaly, abnormal ultrasound findings in the brain and visceral organs, repeated failure in neonatal hearing screening, suspicious maternal cytomegalovirus infection during pregnancy, and other abnormal findings suggestive of congenital cytomegalovirus infection. Among 2121 newborns, 102 (4.8%) were subject to the urine cytomegalovirus DNA test based on the abovementioned criteria. Of them, three were cytomegalovirus DNA-positive. According to the protocol, the cytomegalovirus DNA-positive rates were 0.14% among the total enrollment of 2121 newborns and 2.9% (3/102) among the targeted newborns. This protocol may overlook congenital cytomegalovirus infection that is asymptomatic or exhibits inapparent clinical manifestations only at birth; however, it is feasible and helps lead to the diagnosis of congenital cytomegalovirus infection that may otherwise be overlooked.