(A) SARS-CoV-2 positive tests during March, 2020, according to publicly available data.22-24 SARS-CoV-2 testing began at Yale New Haven Hospital on March 13, 2020. Screening was performed between March 3 and March 14, 2020. (B) In all negative samples on the multiplex viral PCR panel, CXCL10 was measured by ELISA (biomarker-based screening) and SARS-CoV-2 (N1 gene) was measured by RT-qPCR. (C) Four discovered SARS-CoV-2 positive samples shown (red) with corresponding NextStrain codes. The dotted line indicates the proportion of samples with nasopharyngeal CXCL10 concentration of 100 pg/mL or higher.