Lower prevalence of congenital cytomegalovirus infection in Portugal: possible impact of COVID-19 lockdown?

Cytomegalovirus (CMV) is the most frequent cause of congenital infection all over the world. Its prevalence ranges from 0.2 to 2.2%. Transmission from children to their pregnant mothers is a well-known risk factor, particularly if they attend a childcare centre. This study aims to compare the prevalence of CMV congenital infection (CMV_CI) in Portugal (Lisbon) between two studies, performed respectively in 2019 and 2020. In the 2019 study, performed in two hospitals, we found a 0.67% CMV_CI prevalence, using a pool strategy previously tested with saliva samples. In the 2020 study, using the same pool approach in four hospitals (the previous and two additional), and based on 1277 samples, the prevalence was 0.078%.Conclusion: The close temporal coincidence with COVID-19 lockdown suggests that these measures may have had a significant impact on this reduction, although other explanations cannot be ruled-out. What is Known: • Cytomegalovirus is the leading cause of congenital infection. • Behavioural measures decrease cytomegalovirus seroconversion in pregnant women. What is New: • From 2019 to 2020 there was a significant reduction in the prevalence of congenital CMV infection.

Saliva pools for screening of human cytomegalovirus using real-time PCR.

Human cytomegalovirus (HCMV) is the leading congenital infection agent in the world. The importance of screening this infection has been debated, as 10-15% of the asymptomatic newborns with HCMV at birth will present late sequelae. The aim of this study was to test the feasibility of using saliva pools from newborns in a screening program for congenital HCMV infection, in two Portuguese hospitals. The screening was based on the use of pools of 10 saliva samples for detection of viral DNA by real-time PCR. Whenever there was a positive pool, the samples were tested individually, and for each positive sample the result was confirmed with a urine sample collected in the first 2 weeks of life. The study involved 1492 newborns. One hundred and fifty pools were screened, with 14 positive results in saliva, but only 10 were confirmed in urine samples, giving a prevalence of congenital HCMV infection in both hospitals of 0.67% (CI95% 0.36 to 1.23%).Conclusion: The overall prevalence of congenital HCMV infection in both hospitals was 0.67%. The use of saliva pools proved to be effective for the screening of this congenital infection, allowing timely screening and confirmation in a large population, with associated cost reduction. What is Known: • Newborn screening for HCMV is desirable. • Saliva is a good and practical sample. What is New: • The feasibility of using saliva pools for a large-scale screening. • The cost reduction of this strategy.