CRP and infection: CRP (AUC = 0.95; 95% CI: 0.88–1) and serum ferritin (AUC = 0.94; 95% CI: 0.87–1) followed by D-dimer (AUC = 0.8; 95% CI: 0.6–1) had significantly better accuracies in predicting severe illnesses than those with mild–moderate infections.