Although the majority of infected persons are asymptomatic and/or mildly symptomatic, critically ill patients manifest pathological symptoms, such as ground glass opacity in lungs, decreased lymphocytes (lymphocytopenia), increased neutrophils (neutrophilia/neutrophilic leukocytosis), and cytokine storms owing to higher concentration of inflammatory cytokines; namely, TGF-α, TGF-β, IP10, MIP1A, IL-1RA, IL-6, GCSF, MCP-1, and indole 2,3 dioxygenase (IDO) [40,41]. This evidence concerns the gene IDO1 and lymphopenia.