CCL2 and COVID-19: Another characteristic of severe COVID-19 patients is the cytokine storm: over-production of numerous cytokines and chemokines such as interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), monocyte chemotactic protein-1 (CCL2), and chemokine (C-X-C motif) ligand 10 (CXCL10) (Merad et al., 2020).