Incidence of congenital cytomegalovirus infection in Ireland: implications for screening and diagnosis

Background: Congenital cytomegalovirus (cCMV) causes serious intrauterine infection and is the leading cause of sensorineural hearing loss. In the absence of routine screening, asymptomatic infections, which constitute approximately 90% of all cCMV cases, remain undiagnosed; however many clinical abnormalities manifest later in childhood.

Objectives: The aims of the present study were to determine, for the first time, the incidence of cCMV infection in a large maternity hospital in Dublin city and the optimal sampling method for neonatal screening.

Study design: A pilot screening study of asymptomatic infants born was conducted over a 12-month period. Mothers were consented and neonates screened for evidence of CMV infection (n=1044). Urine or saliva was tested for the presence of CMV DNA and reactive results were confirmed with follow-up testing and clinical evaluation.

Results: cCMV incidence in the asymptomatic neonates screened was 0.19%. An overall cCMV incidence was extrapolated based on the total number of live-births and data from those infants routinely screened for cCMV during the study period, and estimated as 0.23%. Neonatal urine collection proved prohibitive to mass screening. However, testing of saliva for CMV DNA was rapid, sensitive and suitable for screening. Furthermore, in a low prevalence population, pooling of patient samples proved effective and cost-efficient.

Conclusions: The present study concluded that there is a significant burden of undiagnosed cCMV infection in Ireland. The introduction of neonatal CMV DNA testing of saliva is viable, and could be considered as part of the national newborn screening programme, following a cost-benefit analysis.