CXCL10 and infection: Although the focus of this study was detecting undiagnosed respiratory viruses, we also found three instances of elevated nasopharyngeal CXCL10 in patients with acute cytomegalovirus or acute Epstein-Barr virus, suggesting that nasopharyngeal CXCL10 might be a biomarker for these infections, which acutely infect the respiratory tract, among other sites, but are usually diagnosed by serology.26,27 Furthermore, we found a distinct nasopharyngeal transcriptomic signature in some CXCL10-high samples associated with neutrophil infiltration and high amounts of airway bacterial pathobionts.