Initial viral load and decay kinetics of SARS-CoV-2 lineage B.1.1.7 in the upper respiratory tract of adults and children

We read with interest the systematic review published by Walsh et al. in the Journal of Infection,1 focusing on the dynamics of SARS-CoV-2 RNA at the upper respiratory tract (URT). In this context, a novel SARS-CoV-2 variant lineage (B.1.1.7), first detected in the UK at the end of 2020 has transmission advantage over other lineages.2 Increased transmissibility of the B.1.1.7 variant has been linked to enhanced ACE2 affinity3 allegedly resulting in higher viral loads in URT, an observation that has been reported in some,3, 4, 5, 6 but not all7 large series published to date. In addition, longer duration of SARS-CoV-2 RNA shedding in URT has been reported in individuals infected by the B.1.1.7 variant as compared to controls;8 if proven, this may have important implications regarding isolation policies. The current retrospective, observational study was undertaken to gain further insight into the above issues. It included a convenience sample of 990 individuals (799 aged >18 years; 507 females) testing positive for SARS-CoV-2 RNA in nasopharyngeal specimens (NP) by the TaqPath COVID-19 Combo Kit (Thermo Fisher Scientific, MS, USA) between June 2020 and April 2021. The study was approved by INCLIVA Research Ethics Committee. A total of 338 subjects (median age, 38 years; range, 1–93 years) were infected by the SARS-CoV-2 lineage B.1.1.7 (179 had COVID-19-Supplementary Table 1). The study included a control group of 652 individuals, 339 presenting with COVID-19 (median age, 40.6 years; range, 0–95 years) infected by other variants, of which 390 were characterized by whole-genome sequencing (Supplementary Table 2). Individuals belonging to the control group were matched with the B.1.1.7 group for sex and age. Among patients with COVID-19, the time from symptoms onset to RT-PCR testing was 5 days (range, 1–10 days) in the B.1.1.7 group and 4 days (range, 1–10 days) in the control group, with no differences between children and adults. As for asymptomatic individuals (140 infected by the B.1.1.7 variant), RT-PCR testing was performed within the first 10 days since diagnosis (for household) or contact with (for non-household) the index case in individuals from both groups. A total of 1152 NP specimens (median 1 specimen/patient; range, 1–3) were included in the analyses described below.Peer reviewe