Upper respiratory tract SARS-CoV-2 RNA loads in symptomatic and asymptomatic children and adults

Costa, Rosa; Bueno, Felipe; Albert, Eliseo; Torres, Ignacio; Carbonell-Sahuquillo, Silvia; Barrés-Fernández, Ana; Sánchez, David; Padrón, Carmelo; Colomina, Javier; Lázaro Carreño, María Isabel; Bretón-Martínez, José Rafael; Martínez-Costa, Cecilia; Navarro, David

OBJECTIVES: Studies comparing SARS-CoV-2 RNA load in the upper respiratory tract (URT) between children and adults, either presenting with COVID-19 or asymptomatic have yielded inconsistent results. Here, we conducted a retrospective, single center study to address this issue. PATIENTS AND METHODS: 1,184 consecutive subjects (256 children and 928 adults) testing positive for SARS-COV-2 RNA in nasopharyngeal exudates (NP), of whom 424 (121 children and 303 adults) had COVID-19 and 760 (135 children and 625 adults) were asymptomatic close contacts of COVID-19 patients. SARS-CoV-2 RNA testing was carried out using the TaqPath COVID-19 Combo Kit (Thermo Fisher Scientific, MS, USA). The AMPLIRUN® TOTAL SARS-CoV-2 RNA Control (Vircell SA, Granada, Spain) was used for estimating SARS-CoV-2 RNA loads (in copies/mL). SARS-CoV-2 RNA loads at the time of laboratory diagnosis (single specimen/patient) were used for comparison purposes. RESULTS: Median initial SARS-COV-2 RNA load was lower (P=0.094) in children (6.98 log(10) copies/ml; range, 3.0-11.7) than in adults (7.14 log(10) copies/ml; range, 2.2.-13.4) with COVID-19. As for asymptomatic individuals, median SARS-CoV-2 RNA load was comparable (P=0.97) in children (6.20 log(10) copies/ml; range, 1.8-11.6) and adults (6.48 log(10) copies/ml; range, 1.9-11.8). Children with COVID-19 symptoms displayed SARS-CoV-2 RNA loads (6.98 log(10) copies/ml; range, 3.0-11.7) comparable to their asymptomatic counterparts (6.20 log(10) copies/ml; range, 1.8-11.6) (P=0.61). Meanwhile in adults, median SARS-CoV-2 RNA load was significantly higher in symptomatic (7.14 log(10) copies/ml; range, 2.2.-13.4) than in asymptomatic subjects (6.48 log(10) copies/ml; range, 1.9-11.8) (P=<0.001). Overall, a faster URT SARS-CoV-2 RNA clearance rate was observed in children than in adults. CONCLUSIONS: Based on viral load data at the time of diagnosis, our results suggested that SARS-CoV-2 infected children, with or without COVID-19, may display NP viral loads of comparable magnitude to that found in their adult counterparts; However, children may have shorter viral shedding as compared to adults.