A protein-protein interaction network of DEGs shared between COVID-19, MERS, SARS, H1N1, and Ebola identifies ICAM1, VEGFA, MMP9, IL6, TNF, IL-8, IL1B, STAT1, TLR2, TLR1, IRF7, and CXCL1 as hub genes (Alsamman and Zayed, 2020). Here, MMP9 is linked to COVID-19.