NET markers, including cell-free DNA (cfDNA), histones (cit-H3), and myeloperoxidase (MPO), are elevated in COVID-19 and correlate with disease severity (49), serum of individuals infected with SARS-CoV-2 can induce NETosis (139, 140), and in vitro studies have shown SARS-CoV-2 directly infecting neutrophils and inducing NETosis (141, 142). Here, MPO is linked to COVID-19.