Initial studies demonstrated that COVID-19 severity is directly correlated with serum levels of pro-inflammatory cytokines, including interleukin (IL) 6 (IL-6) and IL-1 beta (IL-1β), as well as IL-2, IL-8, IL-17, granulocyte colony-stimulating factor (G-CSF), granulocyte macrophage-colony stimulating factor (GM-CSF), human interferon-inducible protein 10 (IP10), monocyte chemotactic protein-1 (MCP1), chemokine (C-C motif) ligand 3 (CCL3), and tumour necrosis factor (TNF) (12, 13). Here, CSF3 is linked to COVID-19.