The variability in disease severity between patients has been linked to differences in the host inflammatory response to the virus infection, with severe COVID-19 patients having increased levels of proinflammatory cytokines (e.g., IL-6 and TNFα) and chemokines (e.g., CCL2 and CXCL10) compared to patients with a mild level of the disease [10,34,35,36,37,38,39]. The gene discussed is CCL2; the disease is COVID-19.