Letter to the Editor on the original article: Lower prevalence of congenital cytomegalovirus infection in Portugal: possible impact of COVID-19 lockdown?

Dear Editor,

We read with interest the article by Fernandez et al. [1], in which the authors describe an eightfold decrease (from 0.67 to 0.078%) in the prevalence of congenital Cytomegalovirus infection (cCMV) in Portugal during the COVID-19 pandemic. We would like to share the preliminary results of an ongoing universal screening study of cCMV in Hospital Sant Joan de Déu (Barcelona, Spain). The study was approved by the local Ethics Committee (ref. PIC-205–19); informed consent from parents is obtained at inclusion. cCMV screening is performed in saliva samples, obtained using flocked swabs (catalog no. 300267, Deltalab; Rubí, Spain) in the first 14 days of life, by means of the Alethia CMV DNA amplification assay (Meridian Bioscience; Cincinnati, OH) [2]; confirmation of cCMV is performed by PCR in urine samples. Overall, 2735 neonates were included during the first 10 months of the study (February 1 to November 30, 2021), 10 tested positive, and only one case was confirmed in urine. Symptomatic disease at birth led to the diagnosis of one further case (out of 63 patients with clinical indication of cCMV investigation). The prevalence of cCMV was 0.071% (95% confidence interval: 0.020–0.260%).

The prevalence of cCMV in our study is very similar to that reported in Portugal, and far from the 0.6% that has been described in a meta-analysis in high-income countries [3]. Unfortunately, historical estimates of cCMV to compare with from our region are not available, but a recent study in Madrid reported a 0.47% prevalence rate [4]. It is likely that the lockdown measures and behavioral interventions to reduce SARS-CoV-2 transmission in Spain during 2020–2021 also impacted on CMV transmission and cCMV prevalence. In fact, a dramatic decrease in respiratory syncytial virus infections in the 2020 winter season [5] and a re-emergence of enterovirus D68 after easing the lockdown in 2021 [6] have also been reported, both viruses sharing the contact transmission route with CMV. We agree with Fernandez et al. [1] that our findings reinforce the role of behavioral risk reduction interventions to prevent cCMV in pregnant women.