Analysis of SARS-CoV-2 Genomes from Southern California Reveals Community Transmission Pathways in the Early Stage of the US COVID-19 Pandemic

Given the higher mortality rate and widespread phenomenon of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS CoV-2) within the United States (US) population, understanding the mutational pattern of SARS CoV-2 has global implications for detection and therapy to prevent further escalation. Los Angeles has become an epicenter of the SARS-CoV-2 pandemic in the US. Efforts to contain the spread of SARS-CoV-2 require identifying its genetic and geographic variation and understanding the drivers of these differences. For the first time, we report genetic characterization of SARS-CoV-2 genome isolates in the Los Angeles population using targeted next generation sequencing (NGS). Samples collected at Cedars Sinai Medical Center were collected from patients with confirmed SARS-CoV-2 infection. We identified and diagnosed 192 patients by our in-house qPCR assay. In this population, the highest frequency variants were in known mutations in the 5’UTR, AA193 protein, RdRp and the spike glycoprotein. SARS-CoV-2 transmission within the local community was tracked by integrating mutation data with patient postal codes with two predominant community spread clusters being identified. Notably, significant viral genomic diversity was identified. Less than 10% of the Los Angeles community samples resembled published mutational profiles of SARS-CoV-2 genomes from China, while >50% of the isolates shared closely similarities to those from New York State. Based on these findings we conclude SARS-CoV-2 was likely introduced into the Los Angeles community predominantly from New York State but also via multiple other independent transmission routes including but not limited to Washington State and China.