By using canonical correlation analysis (CCA), the gut microbiota composition of 30 patients with COVID-19 was visualized by prognostic groups with five serum cytokines – IFN-γ, IL-2, IL-10, TNF-α, and anti-SARS-CoV-2 S immunoglobulin G (IgG) titers (Figure 2B). Here, IL2 is linked to COVID-19.