For example, TREM1 Signalling (z-score = 3.157; BH p-value = 3.162 × 10–02), STAT3 Pathway (z-score = 0.949; BH p-value = 7.762 × 10–03) and IL-22 signalling (z-score = 1.732; BH p-value = 2.239 × 10–02) were all amongst the pathways upregulated in severe COVID-19 compared to mild COVID-19. Here, TREM1 is linked to COVID-19.