Early pandemic molecular diversity of SARS-CoV-2 in children

Background In the US, community circulation of the SARS-CoV-2 virus likely began in February 2020 after mostly travel-related cases. Children's Hospital of Philadelphia began testing on 3/9/2020 for pediatric and adult patients, and for all admitted patients on 4/1/2020, allowing an early glimpse into the local molecular epidemiology of the virus. Methods We obtained 169 SARS-CoV-2 samples (83 from patients <21 years old) from March through May and produced whole genome sequences. We used genotyping tools to track variants over time and to test for possible genotype associated clinical presentations and outcomes in children. Results Our analysis uncovered 13 major lineages that changed in relative abundance as cases peaked in mid-April in Philadelphia. We detected at least 6 introductions of distinct viral variants into the population. As a group, children had more diverse virus genotypes than the adults tested. No strong differences in clinical variables were associated with genotypes. Conclusions Whole genome analysis revealed unexpected diversity, and distinct circulating viral variants within the initial peak of cases in Philadelphia. Most introductions appeared to be local from nearby states. Although limited by sample size, we found no evidence that different genotypes had different clinical impacts in children in this study. Summary Using sequencing and a novel technique for quantifying SARS-CoV-2 diversity, we investigated 169 SARS-CoV-2 genomes (83 <21 years old). This analysis revealed unexpected diversity especially in children. No clear differences in clinical presentation were associated with the different virus lineages.