3.1 Comparison between H1N1 infected patients and SAR-COV-2 infected patients.
Demographic characteristics, ABO blood group and comorbidities prior to admission of all hospitalized patients are presented in Table 1. The proportions of men and patient blood group were similar in the two groups. The median ages of H1N1 and SAR-COV-2-infected patients were 50.0 years (IQR 30.0-65.0, range 20.0-90.0) and 47.0 years (IQR 33.0-61.0, range 18.0-90.0), respectively (P > .05). The duration from disease onset to admission was longer in H1N1 patients (4.0 vs 3.0, p = 0.001). As for comorbid conditions at admission, cerebrovascular disease, diabetes mellitus, hyperlipidemia and COPD were more common in H1N1-infected populations than those in SAR-COV-2-infected group. There were no significant differences between the groups in proportion of ABO blood group. Clinical symptoms were more frequently shown in H1N1-infected group than SAR-COV-2-infected group at admission except for dry cough and diarrhea. Diarrhea was more common in SAR-COV-2-infected group: (4.02% vs 0.91%, P = .033). The difference in the proportion of fever was the most obvious: (82.73% vs 48.59%, p < .001). In addition, H1N1 patients had higher admission temperature (median 37.8 °C, IQR (36.8-38.2) vs. 37.2 (36.8-37.6); p < .001). The comparison of the results of routine blood tests at admission are shown in table 1. For infection-related biomarkers, C-reactive protein level and procalcitonin level on admission were higher in H1N1 patients (median C-reactive protein level 44.96 mg/L, IQR 20.36-77.75; median procalcitonin level 0.16 ng/mL [0.05-0.61]) than non-ICU patients (median C-reactive protein level 32.08 mg/L [12.08-36.30], p <.001; median procalcitonin level 0.07 ng/mL [0.04-24.7], p= 0.0332).
As for treatment and clinical outcome on the two viruses, SAR-COV-2-infected patients were significantly more frequently received antiviral therapy (84.74% vs 76.82%, p = .029) (table 2), as was oxygen therapy: (62.65% vs 40.91, p < 0.001). Pneumonia and multilobar infiltrates were more frequent occurred in SAR-COV-2-infected patients. SAR-COV-2-infected patients’ median duration of hospital stay was longer than those of H1N1 infected patients: (17.5 days vs 7 days, P < .001). Generally, the rates of adverse clinical events were higher in elder patients (Figure 1). In univariable analysis, the odds of hospitalization outcomes (length of stay in hospital >20 days and pneumonia) in SAR-COV-2-infected patients were higher than in those hospitalized with H1N1 infection, albeit with a lower risk for highest temperature > 39°C during hospitalization. When adjusting for age, sex, comorbidities and smoking history our regression model showed similar results (Figure 2).
3.2 Comparison betweenSAR-COV-2 infected patients andmixed-infected patients.
When comparing SAR-COV-2 infected patients with mixed-infected patients (Table 1), we observed that mixed-infected patients (n=36) tended to be older (median 56.0 years vs 47.0 years, p=0.027), with a higher proportion of patients with more than two comorbidities (25.0% vs 8.84%, P = .004). There were no major differences regarding sex or blood group. Myalgia was more frequent in mixed-infected patients; other symptoms showed no significant difference between the two groups. For comparison of the results of routine blood tests, neutrophil count and C-reactive protein level were significantly higher in mixed-infected patients (median neutrophil count 3.67×109 cells/L; median C-reactive protein level 51.2 mg/L) than patients infected with SAR-COV-2 alone (median neutrophil count 2.83×109 cells/L, P = 0.0081; median C-reactive protein level 32.08 mg/L, P < 0.001) whilst haemoglobin and albumin were in a lower level.
Significantly more mixed-infected patients underwent vasoactive agents therapy and ventilation (table2). The length of hospital stay was longer (20.0 vs 17.5 days, P = 0.02) and the rate of secondary bacterial infections (13.89% vs 3.21%, P = 0.004), admittance to ICU (19.44% vs 5.22%, P = 0.002) and mortality (2.78% vs 0, P = 0.008) were significantly higher in mixed-infected patients.