To determine the alveolar epithelial cell death patterns in COVID-19 patients with or without ARDS, we analyzed the serum levels of full-length (CK18-M65 antigen) and caspase-cleaved (CK18-M30 antigen) cytokeratin 18, which are epithelial total cell death and epithelial apoptosis markers, respectively, in addition to the other several alveolar epithelial and endothelial injury markers. The gene discussed is KRT18; the disease is COVID-19.