Objectives: We aimed to compared the clinical features of acute respiratory distress syndrome (ARDS) induced by COVID-19 and H7N9 virus infections.

Methods: Clinical data of 100 COVID-19 patients and 46 H7N9 patients were retrospectively analyzed.

Results: Elevated inflammatory indices and coagulation disorders were more common in COVID-19-ARDS group than in H7N9-ARDS group. The median interval from illness onset to ARDS development was shorter in H7N9-ARDS. The PaO2/FiO2 level was lower in H7N9-ARDS, while SOFA score was higher in COVID-19-ARDS. The proportion of patients with disseminated intravascular coagulation and liver injury in COVID-19-ARDS and H7N9-ARDS was 45.5% vs 3.1%, and 28.8% vs 50%, respectively (P<0.05). The mean interval from illness onset to death was shorter in H7N9-ARDS. 59.1% patients with H7N9-ARDS died of refractory hypoxemia as against 28.9% with COVID-19-ARDS (P=0.014). Patients with COVID-19-ARDS were more likely to die of septic shock and multiple-organ dysfunction compared to H7N9-ARDS (71.2% vs 36.4%, P=0.005).

Conclusion: H7N9 patients were more susceptible to develop severe ARDS and showed a more acute disease course. COVID-19-ARDS was associated with severe inflammatory response and coagulation dysfunction, while liver injury was more common in H7N9-ARDS. The main causes of death between patients with the two diseases were different.