3.1 Dermatologic feature
As shown in Table 1, the median age of severe COVID-19 patients was 49 years old, which was comparable to that of severe H7N9 patients (54 years old, p>0.05). The proportion of males in severe COVID-19 patients was 69.57%, which was also comparable to that of severe H7N9 patients (65.22%, p>0.05). 26.09% of severe COVID-19 patients has a history of underlying diseases, whereas that of severe H7N9 patients was significantly higher, at 56.52% (p=0.04). The majority of severe H7N9 patients suffered to hypertension (p<0.01). There was no significant difference in the history of diabetes, chronic-airway diseases between the two groups (p>0.05).
3.2 Clinical manifestations at diagnosis
At admission (Table 1), almost all severe H7N9 and severe COVID-19 patients presented with fever and cough (100% vs 100%, 100% vs 82.61%, p>0.05 for each). Furthermore, 86.96%, 47.82% and 30.43% of severe H7N9 patients had dyspnea, myalgia and nasal congestion, which was significantly more than those of severe COVID-19 patients (30.43%, 17.39%, 0, p<0.05 for each). The proportions of pharyngodynia (21.74%) and gastrointestinal symptoms (17.39%) in with severe H7N9 patients were comparable to those of severe COVID-19 patients (8.70%, 8.70%), whereas hemoptysis was less common in both two groups.
3.3 Laboratory results
Over the course of the hospitalization (Table 2), acute kidney injury, acute liver injury occurred in 8.07% and 69.57% of patients with severe H7N9, which was comparable to those of severe COVID-19 patients (13.04%, 78.26%, p>0.05 for each). However, 69.57% of severe H7N9 patients suffered to acute cardiac injury, which was significantly higher than the proportion of 4.34% in severe COVID-19 patients (p<0.01). Following biochemical testing, the peak level of alanine aminotransferase (ALT), total bilirubin (TBIL), creatinine (Cr), and troponin I (TnI) in severe COVID-19 patients were comparable to those in severe H7N9 patients (140.9.7±19.11 vs 132.7±19.64 U/L, 22.18±2.80 vs 21.19±1.62 μmol/L, 79.52±5.22 vs 71.74±3.72 μmol/L, 18.65±9.36 vs 286.50±181.1pg/ml, respectively, p>0.05 for each).
Both severe COVID-19 and severe H7N9 patients exhibited impairments in coagulation. However, significantly increase of peak levels of D-dimer and Prothrombin time (PT) were associated with severe H7N9 patients compared to severe COVID-19 patients (5447±1094 vs 1914±426.5 mg/L, 14.67±0.74 vs 12.47±0.17 sec, p<0.05 for each).
In terms of blood cell counting, lymphopenia was observed in most severe COVID-19 (86.96%) and severe H7N9 patients (100%, p>0.05), but the minimal level of lymphocytes in severe COVID-19 patients were higher than those in severe H7N9 patients (0.71±0.06 vs 0.44±0.39 ×109/L, p<0.05). Thrombocytopenia was observed in 47.82% of severe COVID-19 and 65.28% of severe H7N9 patients (p<0.05), but the minimal level of platelet in severe COVID-19 patients were comparable to those in severe H7N9 patients (157.80±11.34 vs 149.20±18.67 ×109/L, p=0.69).
Worst Oxygenation Index (OI) during the hospitalization predicts deteriorated respiratory failure. The minimal level of OI in severe COVID-19 patients was 228.30±11.01 mmHg, which was significantly higher than the 113.7±11.18 mmHg of severe H7N9 patients (p<0.05).
3.4 Imaging findings
In terms of imaging characteristics (Table 2), ground-glass opacity in initial chest CTs was common in COVID-19 patients (43.48%) and in H7N9 patients (60.87%, p>0.05). In contrast, consolidation and pleural effusion were more common in H7N9 patients than in COVID-19 patients (p<0.05 for each), crazy-paving pattern was less seen in H7N9 patients (p<0.05).
3.5 Further course and intensive treatment
Over the course of the viral infections (Table 3), septic shock occurred in 13.04% of patients with severe H7N9. There was no significant difference in the duration of onset to ARDS between severe H7N9 and severe COVID-19 patients (8.39±0.59 days, 8.09±0.72 days, p=0.74). The highest sequential organ failure assessment (SOFA) score and pneumonia severity index (PSI) score of severe COVID-19 patients were 3.57±0.31 and 61.22±2.99, respectively, which were lower than the scores of 5.35±0.77 (p=0.04) and 89.96±7.72 (p=0.00) for severe H7N9 patients.
All patients have received medical bundle intervention, including antimicrobial therapy, fluid administration, respiratory support, or steroid therapy.
The two groups presented with a variety of accompanying secondary bacterial infection. 39.13% of severe H7N9 patients had positive culture of pathogen isolated from qualified lower respiratory tract specimens, whereas that of severe COVID-19 patients was significantly lower (8.70%, p<0.05).
In terms of respiratory support, during the entire process of treatment, the proportions of severe H7N9 patients who received non-invasive mechanical ventilation (NIV) was significantly higher than that of COVID-19 patients (69.57% vs 21.74%, p<0.05). The failure rates of NIV in severe H7N9 patients were comparable to than those in COVID-19 patients (4.35% vs 0%, p>0.05).
In addition to treatments above, 82.61% of COVID-19 patients received glucocorticoids, which was comparable to the proportion of 95.65% in H7N9 patients (p>0.05). Low-molecular-weight Heparin was administered in 43.48% of COVID-19 patients, which also was comparable to that administered to H7N9 patients (34.78%, p<0.001).
3.6 Virologic outcomes and prognosis
All of the patients received antiviral therapies. Oseltamivir was administered in all of the H7N9 patients. However, COVID-19 patients had a variety of antiviral treatments, included 43.48% with lopinavir/ritonavir, 8.70% with arbidol, and 47.83% with combination. The duration of severe COVID-19 RNA shedding from the admission was 13.91±1.56 days, which was longer than that of severe H7N9 patients (9.86±0.81 days, p=0.03).
Based on the follow-up of chest CT, the time to beginning absorption on chest CT (TTBAC) was established. Severe H7N9 patients have longer TTBAC than that in severe COVID-19 patients (11.64±0.83 vs 9.13±0.70 days, p=0.02).
In terms of prognoses, although the in-hospital mortality of H7N9 patients with ARDS was 13.04%, it did not reach the statistical significance when compared to COVID-19 patients (0, p<0.001).
3.7 Multivariate analysis
Based on multiple logistic regression analysis, compared with parameters in severe H7N9 patients, severe COVID-19 patients were associated with a lower risk of the presence of severe ARDS (OR 0.964, 95% [CI] 0.931-0.998, p=0.040), but exhibited longer duration of viral shedding (OR 0.734, 95% [CI] 0.550-0.980, p=0.036) than severe H7N9 infection (Table 4).