Overview of multi-omics study of COVID-19. Blue, green, and orange bars indicate healthy controls and moderate and severe COVID-19 patients, respectively. T# indicates the time points of sample collection, and the number on the bars on the top right side indicates the number of patients. Sample collection was performed at a maximum of three and seven junctures for moderate and severe COVID-19 patients, respectively. The bottom panel shows six distinct types of biospecimens and eight distinct types of multi-omics data. COVID-seq indicates COVID-19 viral genome sequencing.