F2 and respiratory system disorder: In the final multivariate logistic regression model, we found that the maximum body temperature during hospitalization ≥ 37.3 °C (OR: 5.24, 95% CI: 2.70–10.16), history of respiratory diseases (OR: 2.43, 95% CI: 1.20–4.92), decreased platelet count (OR: 2.39, 95% CI: 1.04–5.47), NLR > 5.00 (OR: 3.31, 95% CI: 1.74–6.30), increased levels of creatinine (OR: 2.94, 95% CI: 1.44–6.02), LDH (OR: 1.59, 95% CI: 1.16–2.18) and prothrombin time (OR: 2.51, 95% CI: 1.19–5.27) were independently associated with disease progression in severely ill patients (Fig. 2b).