Patients with severe and fatal disease had significantly increased WBC count, and decreased lymphocyte and platelet counts compared to non-severe disease and survivors. Biomarkers of inflammation, cardiac and muscle injury, liver and kidney function and coagulation measures were also significantly elevated in patients with both severe and fatal COVID-19. IL-6 and IL-10 and serum ferritin were strong discriminators for severe disease. Here, IL6 is linked to COVID-19.