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Comment
. 2021 Oct;83(4):496-522.
doi: 10.1016/j.jinf.2021.08.015. Epub 2021 Aug 11.

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

Rosa Costa  1 , Felipe Bueno  1 , Estela Giménez  1 , Alma Bracho  2 , Eliseo Albert  1 , Diego Carretero  1 , Paula de Michelena  1 , Cecilia Martínez-Costa  3 , Fernando González-Candelas  2 , David Navarro  4
Affiliations
Comment

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

Rosa Costa et al. J Infect. 2021 Oct.
No abstract available

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Conflict of interest statement

Declaration of Competing Interest The authors declare no conflicts of interest.

Figures

Fig 1
Fig. 1
Whisker plots depicting initial SARS-CoV-2 RNA loads in nasopharyngeal specimens from individuals infected by either the B.1.1.7 variant or other variants. Participants were sampled at either primary care centers affiliated to the Clínico-Malvarrosa Health Department, which attends 350,000 inhabitants in Northwest Valencia (Spain), or at its tertiary reference hospital (Hospital Clínico Universitario de Valencia, Spain-HCU-). NP were collected by trained nurses, placed in 3 ml of Universal Transport Medium (UTM, Becton Dickinson, Sparks, MD, USA) and delivered to the Microbiology Service of HCU for testing. Specimens were analyzed by RT-PCR within 24 h of receipt. We used the TaqPath COVID-19 Combo Kit (Thermo Fisher Scientific, MS, USA), which targets SARS-CoV-2 ORF1ab, N and S genes, following RNA extraction carried out by using the Applied Biosystems™ MagMAX™ Viral/Pathogen II Nucleic Acid Isolation Kits coupled with Thermo Scientific™ KingFisher Flex automated instrument. The AMPLIRUN® TOTAL SARS-CoV-2 RNA Control (Vircell SA, Granada, Spain) was used as the reference material for estimating SARS-CoV-2 RNA load (in copies/mL, taking RT-PCR CT for the N gene). The B.1.1.7 lineage was confirmed by whole-genome sequencing in 108 cases, whereas in the remaining 230 it was inferred by S-gene target failure (SGTF) in the RT-PCR as within the timeframe of specimen collection (mid-February-April 2021) more than 95% of SGTFs detected in the Clínico-Malvarrosa Health Department belonged to that lineage (not shown). Control individuals were sampled before the SARS-CoV-2 B1.1.7 variant was first detected in our Health Department in early January 2021. Moreover, the SARS-CoV-2 RNA S-gene was detected in NP from all these participants. The data are depicted for all participants (A); adults (B), children (≤18 years old) (C); adults with COVID-19 (D); children with COVID-19 (E) and asymptomatic adults (F). The absence of non-B.1.1.7-infected asymptomatic children in the cohort precluded meaningful comparison of viral loads between these individuals and those infected by other variants. Differences between medians were compared using the Mann-Whitney U test. The Chi-squared test was used for frequency comparisons. Two-sided P-values < 0.05 were considered statistically significant. Statistical analyses were performed using the SPSS v.25 program. P values for comparisons across groups are shown.
Fig 2
Fig. 2
Kinetics of SARS-CoV-2 RNA load in nasopharyngeal specimens from individuals either infected by the B.1.1.7 variant (A) or by other variants (B) through week 3 after diagnosis of SARS-CoV-2 infection. Trajectories of SARS-CoV-2 RNA load in URT were classified as rising or decreasing, as the variation in the viral load between consecutive specimens was > or <0.5 log10 copies/ml (upper limit of intra-assay log10 variation), respectively. SARS-CoV-2 RNA half-life in the upper respiratory tract from individuals either infected by the B.1.1.7 variant or by other variants (C). The kinetics of SARS-CoV-2 RNA clearance followed a logarithmic decay curve in most individuals, expressed by the equation yt=y0e−kt, where y0 is the initial SARS-CoV-2 RNA load, t is time of follow-up specimen sampling since diagnosis (initial RT-PCR result) and k is the decay constant. SARS-CoV-2 RNA load half-life was then calculated using the equation ln2/k. SARS-CoV-2 RNA half-life in URT was calculated only for individuals (25 infected by the B.1.1.7 variant and 56 controls) that met two criteria: (i) displaying a descending trajectory throughout the study period (three weeks); (ii) the follow-up specimen used for calculations was collected within 4–10 days after the initial one. P value for comparisons across groups is shown.
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