Infants have lower RT-PCR cycle threshold for SARS-CoV-2 in comparison with older children and adults

Abstract

Background: The viral dynamics and the role of children in the spread of SARS-CoV-2 are not completely understood. Our aim was to evaluate how RT-PCR Ct values among children with confirmed SARS-CoV-2 compared with that of adult subjects. Methods: Patients (aged from 2 months to [≤]18 years, and adults) with signs and symptoms of acute SARS-CoV-2 infection for less than 7 days, were prospectively enrolled in the study from May to November 2020. All participants performed RT-PCR assay for SARS-CoV-2 detection; Ct values of ORF1ab, N, and S gene-targets, and the average of all the three probes were used as surrogates of viral load. Results: Of the total of 376 participants with confirmed SARS-CoV-2 infection there were 21 infants, 62 children and 293 adults. The RT-PCR Ct values of children under 18 were not significantly different from that of adults, as observed by the analyzed probes (namely ORF1ab, N, and S), and by the mean of all 3 gene-targets. However, infants had significantly lower Ct values compared to children and adults (P = 0.044). Discussion: Ct values for children were not significantly different than that of adults with positive SARS-CoV-2. Interestingly, infants had even lower Ct values when compared to older children and adults. Although viral load is not the only determinant of transmission, infants may play a significant role in the spread of SARS-CoV-2 in the community, especially if or when this population returns to regular daycare activities.