IL33 and COVID-19: Lower hemoglobin levels have been reported in COVID-19 patients [22, 23] and this may be associated with the intensity of the inflammatory process that interferes with the iron metabolism mediated by the increase in IL-6 and by the direct action of pro-inflammatory cytokines such as interferon-γ, IL-1, IL-33, and tumor necrosis factor (TNF)-α on erythropoiesis, characterized by decreased erythrocyte synthesis [24–26].